Helium atom
An illustration of the helium atom, depicting the nucleus (pink) and the electron cloud distribution (black). Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom Electron cloud is a term used if not originally coined by the Nobel Prize laureate and acclaimed educator Richard Feynman in The Feynman Lectures on Physics The nucleus (upper right) is in reality spherically symmetric, although for more complicated nuclei this is not always the case. The black bar is one ångström, equal to 10−10 m or 100,000 fm. An ångström or angstrom (symbol Å) (ˈɔːŋstrəm Swedish: ˈɔ̀ŋstrœm is an internationally recognized non- SI unit of length equal The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International
Classification
 Smallest recognized division of a chemical element
Properties
 Mass range: 1. A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. The atomic mass (ma is the Mass of an atom most often expressed in unified atomic mass units The atomic mass may be considered to be the total mass 67×10-24 to 4. 52×10-22 g Electric charge: zero (neutral), or ion charge Diameter range: 62 pm (He) to 520 pm (Cs) (data page) Components: Electrons and a compact nucleus of protons and neutrons

Relative to everyday experience, atoms are minuscule objects with proportionately tiny masses that can only be observed individually using special instruments such as the scanning tunneling microscope. Scanning tunneling microscope (STM is a powerful technique for viewing surfaces at the atomic level More than 99. 9% of an atom's mass is concentrated in the nucleus,[3] with protons and neutrons having about equal mass. In atoms with too many or too few neutrons relative to the number of protons, the nucleus is unstable and subject to radioactive decay. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. [4] The electrons surrounding the nucleus occupy a set of stable energy levels, or orbitals, and they can transition between these states by the absorption or emission of photons that match the energy differences between the levels. A quantum mechanical system or particle that is bound, confined spacially can only take on certain discrete values of energy as opposed to classical particles which An atomic orbital is a Mathematical function that describes the wave-like behavior of an electron in an atom In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The electrons determine the chemical properties of an element, and strongly influence an atom's magnetic properties. In Physics, magnetism is one of the Phenomena by which Materials exert attractive or repulsive Forces on other Materials.

## History

Main articles: Atomic theory and Atomism

The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny quantities has been around for millennia, but these ideas were founded in abstract, philosophical reasoning rather than experimentation and empirical observation. This article focuses on the historical models of the atom For a history of the study of how atoms combine to form molecules see History of the molecule. In Natural philosophy, atomism is the theory that all the objects in the universe are composed of very small indestructible building blocks - Atoms Or stated in The nature of atoms in philosophy varied considerably over time and between cultures and schools, and often had spiritual elements. Nevertheless, the basic idea of the atom was adopted by scientists thousands of years later because it elegantly explained new discoveries in the field of chemistry. [5]

The earliest references to the concept of atoms date back to ancient India in the 6th century BCE. This article is about the history of South Asia prior to the Partition of British India in 1947 [6] The Nyaya and Vaisheshika schools developed elaborate theories of how atoms combined into more complex objects (first in pairs, then trios of pairs). Nyāya ( Sanskrit ni-āyá, literally "recursion" used in the sense of " Syllogism, inference" is the name given to one of the six orthodox Vaisheshika, or Vaiśeṣika, (Sanskrit वैशॆषिक) is one of the six Hindu schools of Philosophy (orthodox Vedic systems Vaisheshika, or Vaiśeṣika, (Sanskrit वैशॆषिक) is one of the six Hindu schools of Philosophy (orthodox Vedic systems [7] The references to atoms in the West emerged a century later from Leucippus whose student, Democritus, systemized his views. Leucippus or Leukippos ( Greek, first half of 5th century BC was among the earliest philosophers of Atomism, the idea that everything is composed entirely Democritus ( Greek:) was a pre-Socratic Greek Materialist Philosopher (born at Abdera in Thrace ca In approximately 450 BCE, Democritus coined the term átomos (Greek ἄτομος), which means "uncuttable" or "the smallest indivisible particle of matter", i. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly e. , something that cannot be divided. Although the Indian and Greek concepts of the atom were based purely on philosophy, modern science has retained the name coined by Democritus. [5]

Further progress in the understanding of atoms did not occur until the science of chemistry began to develop. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties In 1661, the natural philosopher Robert Boyle published The Sceptical Chymist in which he argued that matter was composed of various combinations of different "corpuscules" or atoms, rather than the classical elements of air, earth, fire and water. For the current in the 19th century German idealism see Naturphilosophie Natural philosophy or the philosophy of nature (from Robert Boyle was a Natural philosopher, chemist physicist inventor and early Gentleman scientist, noted for his work in Physics and Chemistry The Sceptical Chymist or Chymico-Physical Doubts & Paradoxes is the title of Robert Boyle 's masterpiece of scientific literature published in London Many ancient philosophies used a set of archetypal classical "elements" to explain patterns in Nature. [8] In 1789 the term element was defined by the French nobleman and scientific researcher Antoine Lavoisier to mean basic substances that could not be further broken down by the methods of chemistry. [9]

Various atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy (1808)

In 1803, the Englishman John Dalton, an instructor and natural philosopher, used the concept of atoms to explain why elements always reacted in a ratio of small whole numbers—the law of multiple proportions—and why certain gases dissolved better in water than others. John Dalton FRS (6 September 1766 &ndash 27 July 1844 was an English Chemist, Meteorologist and Physicist. John Dalton FRS (6 September 1766 &ndash 27 July 1844 was an English Chemist, Meteorologist and Physicist. In Mathematics, a natural number (also called counting number) can mean either an element of the set (the positive Integers or an In Chemistry, the law of multiple proportions is one of the basic laws and a major tool of chemical measurement ( Stoichiometry) He proposed that each element consists of atoms of a single, unique type, and that these atoms could join to each other, to form chemical compounds. [10][11]

The physicist J. J. Thomson, through his work on cathode rays in 1897, discovered the electron and its subatomic nature, which destroyed the concept of atoms as being indivisible units. Sir Joseph John “JJ” Thomson, OM, FRS (18 December 1856 &ndash 30 August 1940 was a British Physicist and Nobel laureate Cathode rays (also called an electron beam or e-beam) are streams of Electrons observed in Vacuum tubes i [14] Thomson believed that the electrons were distributed throughout the atom, with their charge balanced by the presence of a uniform sea of positive charge (the plum pudding model). The plum pudding model of the Atom by JJ Thomson, who discovered the Electron in 1897 was proposed in 1904 before the discovery of the atomic nucleus

A Bohr model of the hydrogen atom, showing an electron jumping between fixed orbits and emitting a photon of energy with a specific frequency

However, in 1909, researchers under the direction of physicist Ernest Rutherford bombarded a sheet of gold foil with helium ions and discovered that a small percentage were deflected through much larger angles than was predicted using Thomson's proposal. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Ernest Rutherford 1st Baron Rutherford of Nelson, OM, PC, FRS (30 August 1871 – 19 October 1937 was a New Zealand Physicist Rutherford interpreted the gold foil experiment as suggesting that the positive charge of an atom and most of its mass was concentrated in a nucleus at the center of the atom (the Rutherford model), with the electrons orbiting it like planets around a sun. The Geiger-Marsden experiment (also called the Gold foil experiment or the Rutherford experiment) was an experiment done by Hans Geiger and Ernest The Rutherford model or planetary model was a model of the Atom devised by Ernest Rutherford. Positively charged helium ions passing close to this dense nucleus would then be deflected away at much sharper angles. [15]

While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one type of atom at each position on the periodic table. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Radiochemistry is the Chemistry of Radioactive materials where radioactive Isotopes of elements are used to study the properties and Chemical reactions Frederick Soddy ( 2 September 1877 &ndash 22 September 1956) was an English radiochemist. [16] The term isotope was coined by Margaret Todd as a suitable name for different atoms that belong to the same element. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides Margaret Todd (1859 &ndash 1918 was a Scottish writer and doctor who in 1913 suggested the term Isotope to chemist Frederick Soddy. J. J. Thomson created a technique for separating atom types through his work on ionized gases, which subsequently led to the discovery of stable isotopes. [17]

Meanwhile, in 1913, physicist Niels Bohr revised Rutherford's model by suggesting that the electrons were confined into clearly defined orbits, and could jump between these, but could not freely spiral inward or outward in intermediate states. Niels Henrik David Bohr (nels ˈb̥oɐ̯ˀ in Danish 7 October 1885 – 18 November 1962 was a Danish Physicist who made fundamental contributions to understanding [18] An electron must absorb or emit specific amounts of energy to transition between these fixed orbits. When the light from a heated material is passed through a prism, it produced a multi-colored spectrum. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 In Optics, a prism is a transparent optical element with flat polished surfaces that refract Light. A spectrum (plural spectra or spectrums) is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The appearance of fixed lines in this spectrum was successfully explained by the orbital transitions. A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared [19]

In 1926, Erwin Schrödinger, using Louis de Broglie's 1924 proposal that particles behave to an extent like waves, developed a mathematical model of the atom that described the electrons as three-dimensional waveforms, rather than point particles. Louis-Victor-Pierre-Raymond 7th duc de Broglie, FRS (də bʁœj ( August 15 1892 &ndash March 19 1987) was a French waveformogg|right|a sine square and sawtooth wave at 440 hz]] Waveform means the shape and form of a signal such as a Wave moving in a solid liquid or gaseous A consequence of using waveforms to describe electrons is that it is mathematically impossible to obtain precise values for both the position and momentum of a particle at the same time; this became known as the uncertainty principle. In Geometry, Topology and related branches of mathematics a spatial point describes a specific point within a given space that consists of neither Volume In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product In Quantum physics, the Heisenberg uncertainty principle states that locating a particle in a small region of space makes the Momentum of the particle uncertain In this concept, for each measurement of a position one could only obtain a range of probable values for momentum, and vice versa. Although this model was difficult to visually conceptualize, it was able to explain observations of atomic behavior that previous models could not, such as certain structural and spectral patterns of atoms larger than hydrogen. A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared Thus, the planetary model of the atom was discarded in favor of one that described orbital zones around the nucleus where a given electron is most likely to exist. [20][21]

Schematic diagram of a simple mass spectrometer

The development of the mass spectrometer allowed the exact mass of atoms to be measured. Mass spectrometry is an analytical technique that identifies the chemical composition of a compound or sample based on the Mass-to-charge ratio of charged particles The device uses a magnet to bend the trajectory of a beam of ions, and the amount of deflection is determined by the ratio of an atom's mass to its charge. The chemist Francis William Aston used this instrument to demonstrate that isotopes had different masses. Francis William Aston ( September 1 1877 &ndash November 20 1945) was a British Chemist and Physicist who won the The mass of these isotopes varied by integer amounts, called the whole number rule. The Whole Number Rule states that the masses of the elements are whole number multiples of the mass of the Hydrogen atom [22] The explanation for these different atomic isotopes awaited the discovery of the neutron, a neutral-charged particle with a mass similar to the proton, by the physicist James Chadwick in 1932. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive Sir James Chadwick, CH (20 October 1891 &ndash 24 July 1974 was an English Physicist and Nobel laureate in physics awarded for his discovery of the Isotopes were then explained as elements with the same number of protons, but different numbers of neutrons within the nucleus. [23]

In the 1950s, the development of improved particle accelerator and particle detectors allowed scientists to study the impacts of atoms moving at high energies. In experimental and applied Particle physics and Nuclear engineering, a particle detector, also known as a radiation detector, is a device used to [24] Neutrons and protons were found to be hadrons, or composites of smaller particles called quarks. In Particle physics, a hadron ( from the ἁδρός hadrós, " stout, thick " ( In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. Standard models of nuclear physics were developed that successfully explained the properties of the nucleus in terms of these sub-atomic particles and the forces that govern their interactions. [25]

Around 1985, Steven Chu and co-workers at Bell Labs developed a technique for lowering the temperatures of atoms using lasers. Steven Chu ( Chinese: 朱棣文 Pinyin: Zhū Dìwén (b February 28[[ 948]] St Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is the Research organization A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. In the same year, a team led by William D. Phillips managed to contain atoms of sodium in a magnetic trap. William Daniel Phillips (born November 5, 1948 in Wilkes-Barre Pennsylvania) is an American Physicist. A magnetic trap uses a magnetic gradient in order to trap neutral particles with a Magnetic moment. The combination of these two techniques and a method based on the Doppler effect, developed by Claude Cohen-Tannoudji and his group, allows small numbers of atoms to be cooled to several microkelvin. The Doppler effect (or Doppler shift) named after Christian Doppler, is the change in Frequency and Wavelength of a Wave for Claude Cohen-Tannoudji (born April 1, 1933) is a French Physicist working at the École Normale Supérieure in Paris The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic This allows the atoms to be studied with great precision, and later led to the discovery of Bose-Einstein condensation. A Bose–Einstein condensate (BEC is a State of matter of Bosons confined in an external Potential and cooled to Temperatures very near to [26]

Historically, single atoms have been prohibitively small for scientific applications. Recently, devices have been constructed that use a single metal atom connected through organic ligands to construct a single electron transistor. In Chemistry, a ligand is either an Atom, Ion, or Molecule (see also Functional group) that bonds to a central metal generally In physics a Coulomb blockade, named after Charles-Augustin de Coulomb, is the increased resistance at small bias voltages of an electronic device comprising [27] Experiments have been carried out by trapping and slowing single atoms using laser cooling in a cavity to gain a better physical understanding of matter. Laser cooling is a technique that uses Light to cool atoms to a very low temperature [28]

## Components

### Subatomic particles

Main article: Subatomic particle

Though the word atom originally denoted a particle that cannot be cut into smaller particles, in modern scientific usage the atom is composed of various subatomic particles. A subatomic particle is an elementary or composite Particle smaller than an Atom. A subatomic particle is an elementary or composite Particle smaller than an Atom. The constituent particles of an atom consist of the electron, the proton and, for atoms other than hydrogen-1, the neutron. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron.

The electron is by far the least massive of these particles at 9. 11×10−28 g, with a negative electrical charge and a size that is too small to be measured using available techniques. Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. [29] Protons have a positive charge and a mass 1,836 times that of the electron, at 1. 6726×10−24 g, although this can be reduced by changes to the atomic binding energy. Binding energy is the Mechanical energy required to disassemble a whole into separate parts Neutrons have no electrical charge and have a free mass of 1,839 times the mass of electrons,[30] or 1. 6929×10−24 g. Neutrons and protons have comparable dimensions—on the order of 2. 5×10−15 m—although the 'surface' of these particles is not sharply defined. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International [31]

In the Standard Model of physics, both protons and neutrons are composed of elementary particles called quarks. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. The quark is a type of fermion, one of the two basic constituents of matter—the other being the lepton, of which the electron is an example. In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their There are six types of quarks, and each has a fractional electric charge of either +2/3 or −1/3. Protons are composed of two up quarks and one down quark, while a neutron consists of one up quark and two down quarks. The up quark is a particle described by the Standard Model theory of Physics. The down quark is a first-generation Quark with a charge of -(1/3 e. This distinction accounts for the difference in mass and charge between the two particles. The quarks are held together by the strong nuclear force, which is mediated by gluons. In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and Gluons ( Glue and the suffix -on) are Elementary particles that cause Quarks to interact and are indirectly responsible for the The gluon is a member of the family of bosons, which are elementary particles that mediate physical forces. In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein In Physics, a force is whatever can cause an object with Mass to Accelerate. [32][33]

### Nucleus

Main article: Atomic nucleus

All of the bound protons and neutrons in an atom make up a tiny atomic nucleus, and are collectively called nucleons. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom In Physics a nucleon is a collective name for two Baryons the Neutron and the Proton. The radius of a nucleus is approximately equal to $\begin{smallmatrix}1.07 \cdot \sqrt[3]{A}\end{smallmatrix}$ fm, where A is the total number of nucleons. [34] This is much smaller than the radius of the atom, which is on the order of 105 fm. The nucleons are bound together by a short-ranged attractive potential called the residual strong force. The nuclear force (or nucleon-nucleon interaction or residual strong force) is the force between two or more Nucleons It is responsible for At distances smaller than 2. 5 fm, this force is much more powerful than the electrostatic force that causes positively charged protons to repel each other. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International ---- Bold text Coulomb's law', developed in the 1780s by French physicist Charles Augustin de Coulomb, may be stated in scalar form [35]

Atoms of the same element have the same number of protons, called the atomic number. A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton Within a single element, the number of neutrons may vary, determining the isotope of that element. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides The total number of protons and neutrons determine the nuclide. A nuclide (from lat nucleus is a species of Atom characterized by the constitution of its nucleus and hence by the number of Protons, the number of The number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing radioactive decay. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. [36]

The neutron and the proton are different types of fermions. In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. The Pauli exclusion principle is a quantum mechanical effect that prohibits identical fermions (such as multiple protons) from occupying the same quantum physical state at the same time. The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925 Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Thus every proton in the nucleus must occupy a different state, with its own energy level, and the same rule applies to all of the neutrons. (This prohibition does not apply to a proton and neutron occupying the same quantum state. )[37]

A nucleus that has a different number of protons than neutrons can potentially drop to a lower energy state through a radioactive decay that causes the number of protons and neutrons to more closely match. As a result, atoms with matching numbers of protons and neutrons are more stable against decay. However, with increasing atomic number, the mutual repulsion of the protons requires an increasing proportion of neutrons to maintain the stability of the nucleus, which slightly modifies this trend of equal numbers of protons to neutrons. [37]

This diagram illustrates a nuclear fusion process that forms a deuterium nucleus, consisting of a proton and a neutron, from two protons. A positron (e+)—an antimatter electron—is emitted along with an electron neutrino. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. In Particle physics and Quantum chemistry, antimatter is the extension of the concept of the Antiparticle to Matter, where antimatter is composed Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost

The number of protons and neutrons in the atomic nucleus can be modified, although this can require very high energies because of the strong force. Nuclear fusion occurs when multiple atomic particles join to form a heavier nucleus, such as through the energetic collision of two nuclei. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus At the core of the Sun, protons require energies of 3–10 KeV to overcome their mutual repulsion—the coulomb barrier—and fuse together into a single nucleus. The Coulomb barrier, named after physicist Charles-Augustin de Coulomb (1736&ndash1806 is the energy barrier due to Electrostatic interaction that two nuclei need [38] Nuclear fission is the opposite process, causing a nucleus to split into two smaller nuclei—usually through radioactive decay. Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei) often producing Free neutrons and other smaller nuclei which may The nucleus can also be modified through bombardment by high energy subatomic particles or photons. In such processes that change the number of protons in a nucleus, the atom becomes an atom of a different chemical element. [39][40]

The mass of the nucleus following a fusion reaction is less than the sum of the masses of the separate particles. The difference between these two values is emitted as energy, as described by Albert Einstein's mass–energy equivalence formula, E = mc², where m is the mass loss and c is the speed of light. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical In Physics, mass–energy equivalence is the concept that for particles slower than light any Mass has an associated Energy and vice versa. This deficit is the binding energy of the nucleus. Binding energy is the Mechanical energy required to disassemble a whole into separate parts [41]

The fusion of two nuclei that have lower atomic numbers than iron and nickel is an exothermic process that releases more energy than is required to bring them together. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 An exothermic reaction is a Chemical reaction that releases Heat. [42] It is this energy-releasing process that makes nuclear fusion in stars a self-sustaining reaction. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth For heavier nuclei, the total binding energy begins to decrease. That means fusion processes with nuclei that have higher atomic numbers is an endothermic process. In Thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs Energy in the form of Heat. These more massive nuclei can not undergo an energy-producing fusion reaction that can sustain the hydrostatic equilibrium of a star. Hydrostatic equilibrium occurs when compression due to Gravity is balanced by a Pressure gradient which creates a Pressure gradient force in the opposite [37]

### Electron cloud

Main article: Electron cloud
This is an example of a potential well, showing the minimum energy V(x) needed to reach each position x. Electron cloud is a term used if not originally coined by the Nobel Prize laureate and acclaimed educator Richard Feynman in The Feynman Lectures on Physics A particle with energy E is constrained to a range of positions between x1 and x2.

The electrons in an atom are attracted to the protons in the nucleus by the electromagnetic force. In Physics, the electromagnetic force is the force that the Electromagnetic field exerts on electrically charged particles This force binds the electrons inside an electrostatic potential well surrounding the smaller nucleus, which means that an external source of energy is needed in order for the electron to escape. Electrostatics is the branch of Science that deals with the Phenomena arising from what seems to be stationary Electric charges Since Classical A potential well is the region surrounding a Local minimum of Potential energy. The closer an electron is to the nucleus, the greater the attractive force. Hence electrons bound near the center of the potential well require more energy to escape than those at the exterior.

Electrons, like other particles, have properties of both a particle and a wave. In Physics and Chemistry, wave–particle duality is the concept that all Matter and Energy exhibits both Wave -like and The electron cloud is a region inside the potential well where each electron forms a type of three-dimensional standing wave—a wave form that does not move relative to the nucleus. A standing wave, also known as a stationary wave, is a Wave that remains in a constant position This behavior is defined by an atomic orbital, a mathematical function that characterises the probability that an electron will appear to be at a particular location when its position is measured. An atomic orbital is a Mathematical function that describes the wave-like behavior of an electron in an atom Only a discrete (or quantized) set of these orbitals exist around the nucleus, as other possible wave patterns will rapidly decay into a more stable form. [43] Orbitals can have one or more ring or node structures, and they differ from each other in size, shape and orientation. [44]

This illustration shows the wave functions of the first five atomic orbitals. Note how each of the three 2p orbitals display a single angular node that has an orientation and a minimum at the center. A node is a point along a Standing wave where the wave has minimal Amplitude.

Each atomic orbital corresponds to a particular energy level of the electron. A quantum mechanical system or particle that is bound, confined spacially can only take on certain discrete values of energy as opposed to classical particles which The electron can change its state to a higher energy level by absorbing a photon with sufficient energy to boost it into the new quantum state. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Likewise, through spontaneous emission, an electron in a higher energy state can drop to a lower energy state while radiating the excess energy as a photon. Spontaneous emission is the process by which a light source such as an Atom, Molecule, Nanocrystal or nucleus in an Excited state These characteristic energy values, defined by the differences in the energies of the quantum states, are responsible for atomic spectral lines. In Physics, atomic Spectral lines are of two types An emission line is formed when an electron makes a transition from a particular discrete [43]

The amount of energy needed to remove or add an electron (the electron binding energy) is far less than the binding energy of nucleons. Electron binding energy (BE is the energy required to release an electron from its atomic or molecular orbital Binding energy is the Mechanical energy required to disassemble a whole into separate parts For example, it requires only 13. 6 eV to strip a ground-state electron from a hydrogen atom. In Quantum mechanics, a stationary state is an Eigenstate of a Hamiltonian, or in other words a state of definite energy [45] Atoms are electrically neutral if they have an equal number of protons and electrons. Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. Atoms that have either a deficit or a surplus of electrons are called ions. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Electrons that are farthest from the nucleus may be transferred to other nearby atoms or shared between atoms. By this mechanism, atoms are able to bond into molecules and other types of chemical compounds like ionic and covalent network crystals. A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. An ionic crystal is a Crystal consisting of Ions bound together by their Electrostatic attraction Crystallization is the (natural or artificial process of formation of solid Crystals precipitating from a homogeneous --> identical Solution [46]

## Properties

### Nuclear properties

Main article: isotope

By definition, any two atoms with an identical number of protons in their nuclei belong to the same chemical element. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. Atoms with the same number of protons but a different number of neutrons are different isotopes of the same element. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides Hydrogen atoms, for example, always have only a single proton, but isotopes exist with no neutrons (hydrogen-1, sometimes called protium, by far the most common form), one neutron (deuterium) and two neutrons (tritium). A hydrogen atom is an atom of the chemical element Hydrogen. The electrically neutral Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. [47] The known elements form a continuous range of atomic numbers from hydrogen with a single proton up to the 118-proton element ununoctium. Ununoctium (ˌjuːnəˈnɒktiəm or /ˌʌnəˈnɒktiəm/ also known as eka-radon or element 118, is the temporary IUPAC name for [48] All known isotopes of elements with atomic numbers greater than 82 are radioactive. [49][50]

About 339 nuclides occur naturally on Earth, of which 269 (about 79%) are stable. [51] Of the chemical elements, 80 have one or more stable isotopes. Elements 43, 61, and all elements numbered 83 or higher have no stable isotopes. As a rule, there is, for each atomic number (each element) only a handful of stable isotopes, the average being 3. 4 stable isotopes per element which has any stable isotopes. Sixteen elements have only a single stable isotope, while the largest number of stable isotopes observed for any element is ten (for the element tin). Tin is a Chemical element with the symbol Sn (stannum and Atomic number 50 [52]

Stability of isotopes is affected by the ratio of protons to neutrons, and also by presence of certain "magic numbers" of neutrons or protons which represent closed and filled quantum shells. These quantum shells correspond to a set of energy levels within the shell model of the nucleus. In Nuclear physics, the nuclear shell model is a model of the Atomic nucleus which uses the Pauli principle to describe the structure Of the 269 known stable nuclides, only four have both an odd number of protons and odd number of neutrons: 2H, 6Li, 10B and 14N. Also, only four naturally-occurring, radioactive odd-odd nuclides have a half-life over a billion years: 40K, 50V, 138La and 180mTa. Most odd-odd nuclei are highly unstable with respect to beta decay, because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects. In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted In Nuclear physics, the semi-empirical mass formula ( SEMF) sometimes also called Weizsäcker's formula is a formula used to approximate the Mass [52]

### Mass

Main article: Atomic mass

Because the large majority of an atom's mass comes from the protons and neutrons, the total number of these particles in an atom is called the mass number. The atomic mass (ma is the Mass of an atom most often expressed in unified atomic mass units The atomic mass may be considered to be the total mass The mass number ( A) also called atomic mass number or nucleon number, is the total number of Protons and Neutrons (together known as The mass of an atom at rest is often expressed using the unified atomic mass unit (u), which is also called a Dalton (Da). The unified atomic mass unit ( u) or Dalton ( Da) or sometimes universal mass unit, is an unit of Mass used to express This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12, which is approximately 1. Carbon-12 is the most abundant of the two stable Isotopes of the element Carbon, accounting for 98 66×10−24 g. [53] hydrogen-1, the lightest isotope of hydrogen and the atom with the lowest mass, has an atomic weight of 1. A hydrogen atom is an atom of the chemical element Hydrogen. The electrically neutral 007825 u. [54] An atom has a mass approximately equal to the mass number times the atomic mass unit. [55] The heaviest stable atom is lead-208,[49] with a mass of 207. Stable isotopes are chemical isotopes that are not Radioactive (to current knowledge 9766521 u. [56]

As even the most massive atoms are far too light to work with directly, chemists instead use the unit of moles. The mole (symbol mol) is a unit of Amount of substance: it is an SI base unit, and almost the only unit to be used to measure this The mole is defined such that one mole of any element will always have the same number of atoms (about 6.022×1023). The Avogadro constant (symbols L, N A also called Avogadro's number, is the number of "elementary entities" (usually Atoms This number was chosen so that if an element has an atomic mass of 1 u, a mole of atoms of that element will have a mass of 1 g. Carbon, for example, has an atomic mass of 12 u, so a mole of carbon atoms weighs 12 g. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 [53]

### Size

Atoms lack a well-defined outer boundary, so the dimensions are usually described in terms of the distances between two nuclei when the two atoms are joined in a chemical bond. Atomic radius, and more generally the size of an atom, is not a precisely defined Physical quantity, nor is it constant in all circumstances A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic The radius varies with the location of an atom on the atomic chart, the type of chemical bond, the number of neighboring atoms (coordination number) and a quantum mechanical property known as spin. The coordination number of an atom in a molecule or a crystal is the number of its nearest neighbours Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin [57] On the periodic table of the elements, atom size tends to increase when moving down columns, but decrease when moving across rows (left to right). The periodic table of the chemical elements is a tabular method of displaying the Chemical elements Although precursors to this table exist its invention is [58] Consequently, the smallest atom is helium with a radius of 32 pm, while one of the largest is caesium at 225 pm. A picometre ( American spelling: picometer, symbol pm) is a unit of Length in the Metric system, equal to one trillionth Caesium or cesium (ˈsiːziəm is the Chemical element with the symbol Cs and Atomic number 55 [59] These dimensions are thousands of times smaller than the wavelengths of light (400–700 nm) so they can not be viewed using an optical microscope. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a The optical microscope, often referred to as the "light microscope" is a type of Microscope which uses Visible light and a system of lenses to However, individual atoms can be observed using a scanning tunneling microscope. Scanning tunneling microscope (STM is a powerful technique for viewing surfaces at the atomic level

Some examples will demonstrate the minuteness of the atom. A typical human hair is about 1 million carbon atoms in width. [60] A single drop of water contains about 2 sextillion (2×1021) atoms of oxygen, and twice the number of hydrogen atoms. Names of numbers larger than a quadrillion are almost never used for reasons discussed further below [61] A single carat diamond with a mass of 0. The carat is a unit of Mass used for measuring gems and Pearls Currently a carat is defined as exactly 200  mg (0 In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in 2 g contains about 10 sextillion atoms of carbon. Names of numbers larger than a quadrillion are almost never used for reasons discussed further below Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 [62] If an apple was magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple. [63]

This diagram shows the half-life (T½) in seconds of various isotopes with Z protons and N neutrons. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation.

Every element has one or more isotopes that have unstable nuclei that are subject to radioactive decay, causing the nucleus to emit particles or electromagnetic radiation. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Radioactivity can occur when the radius of a nucleus is large compared with the radius of the strong force, which only acts over distances on the order of 1 fm. [64]

There are three primary forms of radioactive decay:[65][66]

• Alpha decay is caused when the nucleus emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons. Alpha decay is a type of radioactive decay in which an Atomic nucleus emits an Alpha particle (two protons and two neutrons bound together into a particle The result of the emission is a new element with a lower atomic number. See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton
• Beta decay is regulated by the weak force, and results from a transformation of a neutron into a proton, or a proton into a neutron. In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature The first is accompanied by the emission of an electron and an antineutrino, while the second causes the emission of a positron and a neutrino. In Physics, antineutrinos, the Antiparticles of Neutrinos are neutral particles produced in nuclear Beta decay. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost The electron or positron emissions are called beta particles. Beta decay either increases or decreases the atomic number of the nucleus by one.
• Gamma decay results from a change in the energy level of the nucleus to a lower state, resulting in the emission of electromagnetic radiation. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions This can occur following the emission of an alpha or a beta particle from radioactive decay.

Each radioactive isotope has a characteristic decay time period—the half-life—that is determined by the amount of time needed for half of a sample to decay. Half-Life (computer-game page here It's already listed in the disambiguation page This is an exponential decay process that steadily decreases the proportion of the remaining isotope by 50% every half life. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value Hence after two half-lives have passed only 25% of the isotope will be present, and so forth. [64]

### Magnetic moment

Elementary particles possess an intrinsic quantum mechanical property known as spin. In Atomic physics, the magnetic dipole moment of an Electron is caused by its intrinsic property of spin within a magnetic field The nuclear magnetic moment is the Magnetic moment of an Atomic nucleus and arises from the spin of the Protons and Neutrons It is mainly a magnetic In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin This is analogous to the angular momentum of an object that is spinning around its center of mass, although strictly speaking these particles are believed to be point-like and cannot be said to be rotating. In Physics, the angular momentum of a particle about an origin is a vector quantity equal to the mass of the particle multiplied by the Cross product of the position Spin is measured in units of the reduced Planck constant ($\hbar$), with electrons, protons and neutrons all having spin ½ $\hbar$, or "spin-½". The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. In an atom, electrons in motion around the nucleus possess orbital angular momentum in addition to their spin, while the nucleus itself possesses angular momentum due to its nuclear spin. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom The Azimuthal quantum number (or orbital angular momentum quantum number, second quantum number) symbolized as l (lower-case L is a Quantum number [67]

The magnetic field produced by an atom—its magnetic moment—is determined by these various forms of angular momentum, just as a rotating charged object classically produces a magnetic field. In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges In Physics, Astronomy, Chemistry, and Electrical engineering, the term magnetic moment of a system (such as a loop of Electric current However, the most dominant contribution comes from spin. Due to the nature of electrons to obey the Pauli exclusion principle, in which no two electrons may be found in the same quantum state, bound electrons pair up with each other, with one member of each pair in a spin up state and the other in the opposite, spin down state. The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925 In Quantum physics, a quantum state is a mathematical object that fully describes a quantum system. Thus these spins cancel each other out, reducing the total magnetic dipole moment to zero in some atoms with even number of electrons. [68]

In ferromagnetic elements such as iron, an odd number of electrons leads to an unpaired electron and a net overall magnetic moment. Ferromagnetism is the basic mechanism by which certain materials (such as Iron) form Permanent magnets and/or exhibit strong interactions with Magnets it The orbitals of neighboring atoms overlap and a lower energy state is achieved when the spins of unpaired electrons are aligned with each other, a process is known as an exchange interaction. In Physics, the exchange interaction is a Quantum mechanical effect which increases or decreases the expectation value of the Energy or Distance When the magnetic moments of ferromagnetic atoms are lined up, the material can produce a measurable macroscopic field. Paramagnetic materials have atoms with magnetic moments that line up in random directions when no magnetic field is present, but the magnetic moments of the individual atoms line up in the presence of a field. Paramagnetism is a form of magnetism which occurs only in the presence of an externally applied magnetic field [69][68]

The nucleus of an atom can also have a net spin. Normally these nuclei are aligned in random directions because of thermal equilibrium. In Thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium Mechanical equilibrium, and However, for certain elements (such as xenon-129) it is possible to polarize a significant proportion of the nuclear spin states so that they are aligned in the same direction—a condition called hyperpolarization. Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations Hyperpolarization is the nuclear spin polarization of a material far beyond Thermal equilibrium conditions This has important applications in magnetic resonance imaging. [70][71]

### Energy levels

When an electron is bound to an atom, it has a potential energy that is inversely proportional to its distance from the nucleus. A quantum mechanical system or particle that is bound, confined spacially can only take on certain discrete values of energy as opposed to classical particles which In Physics, atomic Spectral lines are of two types An emission line is formed when an electron makes a transition from a particular discrete Potential energy can be thought of as Energy stored within a physical system This is measured by the amount of energy needed to unbind the electron from the atom, and is usually given in units of electronvolts (eV). In the quantum mechanical model, a bound electron can only occupy a set of states centered on the nucleus, and each state corresponds to a specific energy level. The lowest energy state of a bound electron is called the ground state, while an electron at a higher energy level is in an excited state. [72]

In order for an electron to transition between two different states, it must absorb or emit a photon at an energy matching the difference in the potential energy of those levels. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The energy of an emitted photon is proportional to its frequency, so these specific energy levels appear as distinct bands in the electromagnetic spectrum. Frequency is a measure of the number of occurrences of a repeating event per unit Time. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies [73] Each element has a characteristic spectrum that can depend on the nuclear charge, subshells filled by electrons, the electromagnetic interactions between the electrons and other factors. [74]

An example of absorption lines in a spectrum

When a continuous spectrum of energy is passed through a gas or plasma, some of the photons are absorbed by atoms, causing electrons to change their energy level. Those excited electrons that remain bound to their atom will spontaneously emit this energy as a photon, traveling in a random direction, and so drop back to lower energy levels. Thus the atoms behave like a filter that forms a series of dark absorption bands in the energy output. An absorption band is a range of Wavelengths (or equivalently frequencies) in the Electromagnetic spectrum which are able to excite a particular (An observer viewing the atoms from a different direction, which does not include the continuous spectrum in the background, will instead see a series of emission lines from the photons emitted by the atoms. A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared ) Spectroscopic measurements of the strength and width of spectral lines allow the composition and physical properties of a substance to be determined. Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared [75]

Close examination of the spectral lines reveals that some display a fine structure splitting. In Atomic physics, the fine structure describes the splitting of the Spectral lines of Atoms due to first order relativistic corrections This occurs because of spin-orbit coupling, which is an interaction between the spin and motion of the outermost electron. In Quantum physics, the spin-orbit interaction (also called spin-orbit effect or spin-orbit coupling) is any interaction of a particle's spin [76] When an atom is in an external magnetic field, spectral lines become split into three or more components; a phenomenon called the Zeeman effect. The Zeeman effect (ˈzeɪmɑːn is the splitting of a Spectral line into several components in the presence of a static Magnetic field. This is caused by the interaction of the magnetic field with the magnetic moment of the atom and its electrons. Some atoms can have multiple electron configurations with the same energy level, which thus appear as a single spectral line. In Atomic physics and Quantum chemistry, electron configuration is the arrangement of Electrons in an Atom, Molecule, or other The interaction of the magnetic field with the atom shifts these electron configurations to slightly different energy levels, resulting in multiple spectral lines. [77] The presence of an external electric field can cause a comparable splitting and shifting of spectral lines by modifying the electron energy levels, a phenomenon called the Stark effect. In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can The Stark effect is the shifting and splitting of Spectral lines of atoms and molecules due to the presence of an external static Electric field. [78]

If a bound electron is in an excited state, an interacting photon with the proper energy can cause stimulated emission of a photon with a matching energy level. In Optics, stimulated emission is the process by which an electron perturbed by a Photon having the correct energy may drop to a lower Energy level resulting For this to occur, the electron must drop to a lower energy state that has an energy difference matching the energy of the interacting photon. The emitted photon and the interacting photon will then move off in parallel and with matching phases. That is, the wave patterns of the two photons will be synchronized. This physical property is used to make lasers, which can emit a coherent beam of light energy in a narrow frequency band. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission. [79]

### Valence

Main article: Valence (chemistry)

The outermost electron shell of an atom in its uncombined state is known as the valence shell, and the electrons in that shell are called valence electrons. In Chemistry, valence, also known as valency or valency number, is a measure of the number of Chemical bonds formed by the Atoms In chemistry valence electrons are the Electrons contained in the outermost or valence, Electron shell of an Atom. The number of valence electrons determines the bonding behavior with other atoms. A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic Atoms tend to chemically react with each other in a manner that will fill (or empty) their outer valence shells. A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called [80]

The chemical elements are often displayed in a periodic table that is laid out to display recurring chemical properties, and elements with the same number of valence electrons form a group that is aligned in the same column of the table. A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. The periodic table of the chemical elements is a tabular method of displaying the Chemical elements Although precursors to this table exist its invention is (The horizontal rows correspond to the filling of a quantum shell of electrons. ) The elements at the far right of the table have their outer shell completely filled with electrons, which results in chemically inert elements known as the noble gases. History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity [81][82]

### States

Main articles: State of matter and Phase (matter)
These snapshots illustrate the formation of a bose-einstein condensate. A state of matter (or physical state, or form of matter) has physical properties which are qualitatively different from other states of matter In the Physical sciences a phase is a Set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties

Quantities of atoms are found in different states of matter that depend on the physical conditions, such as temperature and pressure. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface By varying the conditions, materials can transition between solids, liquids, gases and plasmas. A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of This page is about the physical properties of gas as a state of matter In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound [83] Within a state, a material can also exist in different phases. An example of this is solid carbon, which can exist as graphite or diamond. The Mineral graphite, as with Diamond and Fullerene, is one of the Allotropes of carbon. In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in [84]

At temperatures close to absolute zero, atoms can form a Bose–Einstein condensate, at which point quantum mechanical effects, which are normally only observed at the atomic scale, become apparent on a macroscopic scale. Absolute zero is the point at which molecules do not move (relative to the rest of the body more than they are required to by a quantum mechanical effect called Zero-point A Bose–Einstein condensate (BEC is a State of matter of Bosons confined in an external Potential and cooled to Temperatures very near to [85][86] This super-cooled collection of atoms then behaves as a single Super Atom, which may allow fundamental checks of quantum mechanical behavior. The term super atom is used to refer to either a Bose–Einstein condensate or an integral cluster of metal atoms [87]

## Identification

This scanning tunneling microscope image clearly shows the individual atoms that make up this gold(100) surface. Scanning tunneling microscope (STM is a powerful technique for viewing surfaces at the atomic level Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79 Miller indices are a notation system in Crystallography for planes and directions in crystal (Bravais lattices In particular a family of Lattice planes Reconstruction causes the surface atoms to deviate from the bulk crystal structure and arrange in columns several atoms wide with pits between them. Surface reconstruction refers to the process by which Atoms at the surface of a Crystal assume a different structure than that of the bulk In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal.

The scanning tunneling microscope is a device for viewing surfaces at the atomic level. Scanning tunneling microscope (STM is a powerful technique for viewing surfaces at the atomic level It uses the quantum tunneling phenomenon, which allows particles to pass through a barrier that would normally be insurmountable. In Quantum mechanics, quantum tunnelling is a nanoscopic phenomenon in which a particle violates the principles of Classical mechanics by penetrating a Electrons tunnel through the vacuum between two planar metal electrodes, on each of which is an adsorbed atom, providing a tunneling-current density that can be measured. Scanning one atom (taken as the tip) as it moves past the other (the sample) permits plotting of tip displacement versus lateral separation for a constant current. The calculation shows the extent to which scanning-tunneling-microscope images of an individual atom are visible. It confirms that for low bias, the microscope images the space-averaged dimensions of the electron orbitals across closely packed energy levels—the Fermi level local density of states. The Fermi energy is a concept in Quantum mechanics usually referring to the energy of the highest occupied Quantum state in a system of Fermions at Local density of states (LDOS is a physical quantity that describes the Density of states, but space-resolved [88][89]

An atom can be ionized by removing one of its electrons. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge The electric charge causes the trajectory of an atom to bend when it passes through a magnetic field. Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges The radius by which the trajectory of a moving ion is turned by the magnetic field is determined by the mass of the atom. The mass spectrometer uses this principle to measure the mass-to-charge ratio of ions. Mass spectrometry is an analytical technique that identifies the chemical composition of a compound or sample based on the Mass-to-charge ratio of charged particles The mass-to-charge ratio, is a Physical quantity that is widely used in the Electrodynamics of charged particles e If a sample contains multiple isotopes, the mass spectrometer can determine the proportion of each isotope in the sample by measuring the intensity of the different beams of ions. Techniques to vaporize atoms include inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry, both of which use a plasma to vaporize samples for analysis. Inductively coupled plasma atomic emission spectroscopy (ICP-AES also referred to as inductively coupled plasma optical emission spectrometry (ICP-OES is an analytical technique used ICP-MS ( Inductively coupled plasma mass spectrometry) is a type of Mass spectrometry that is highly sensitive and capable of the determination of a range of Metals [90]

A more area-selective method is electron energy loss spectroscopy, which measures the energy loss of an electron beam within a transmission electron microscope when it interacts with a portion of a sample. In electron energy loss spectroscopy (EELS a material is exposed to a beam of Electrons with a known narrow range of kinetic energies. Cathode rays (also called an electron beam or e-beam) are streams of Electrons observed in Vacuum tubes i The atom-probe tomograph has sub-nanometer resolution in 3-D and can chemically identify individual atoms using time-of-flight mass spectrometry. The atom probe is an atomic-resolution Microscope used in Materials science that was invented in 1967 by Erwin Müller, J [91]

Spectra of excited states can be used to analyze the atomic composition of distant stars. Excitation is an elevation in energy level above an arbitrary baseline energy state A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth Specific light wavelengths contained in the observed light from stars can be separated out and related to the quantized transitions in free gas atoms. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. These colors can be replicated using a gas-discharge lamp containing the same element. Gas discharge lamps are a family of artificial light sources that generate light by sending an Electrical discharge through an ionized gas i [92] Helium was discovered in this way in the spectrum of the Sun 23 years before it was found on Earth. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical [93]

## Origin and current state

Atoms form about 4% of the total mass density of the observable universe, with an average density of about 0. The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy 25 atoms/m3. [94] Within a galaxy such as the Milky Way, atoms have a much higher concentration, with the density of matter in the interstellar medium (ISM) ranging from 105 to 109 atoms/m3. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply [95] The Sun is believed to be inside the Local Bubble, a region of highly ionized gas, so the density in the solar neighborhood is only about 103 atoms/m3. The Local Bubble is a cavity in the Interstellar medium (ISM of the Orion Arm of the Milky Way. [96] Stars form from dense clouds in the ISM, and the evolutionary processes of stars result in the steady enrichment of the ISM with elements more massive than hydrogen and helium. Up to 95% of the Milky Way's atoms are concentrated inside stars and the total mass of atoms forms about 10% of the mass of the galaxy. [97] (The remainder of the mass is an unknown dark matter. In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from [98])

### Nucleosynthesis

Main article: Nucleosynthesis

Stable protons and electrons appeared one second after the Big Bang. Nucleosynthesis is the process of creating new atomic nuclei from preexisting Nucleons (protons and neutrons The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. During the following three minutes, Big Bang nucleosynthesis produced most of the helium, lithium, and deuterium in the universe, and perhaps some of the beryllium and boron. In Physical cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than those of H-1 (i Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Lithium (ˈlɪθiəm is a Chemical element with the symbol Li and Atomic number 3 Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth Beryllium (bəˈrɪliəm is a Chemical element with the symbol Be and Atomic number 4 Boron (ˈbɔərɒn is a Chemical element with Atomic number 5 and the chemical symbol B. [99][100][101] The first atoms (complete with bound electrons) were theoretically created 380,000 years after the Big Bang—an epoch called recombination, when the expanding universe cooled enough to allow electrons to become attached to nuclei. This timeline of the Big Bang describes the events according to the Scientific theory of the Big Bang, using the cosmological time parameter of Comoving coordinates [102] Since then, atomic nuclei have been combined in stars through the process of nuclear fusion to produce elements up to iron. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus [103]

Isotopes such as lithium-6 are generated in space through cosmic ray spallation. Cosmic ray spallation is a form of naturally occurring Nuclear fission and Nucleosynthesis. [104] This occurs when a high-energy proton strikes an atomic nucleus, causing large numbers of nucleons to be ejected. Elements heavier than iron were produced in supernovae through the r-process and in AGB stars through the s-process, both of which involve the capture of neutrons by atomic nuclei. A supernova (plural supernovae or supernovas) is a stellar Explosion. The r-process is a Nucleosynthesis process occurring in core-collapse Supernovae (see also Supernova nucleosynthesis) responsible for the creation of approximately The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass Stars This is a period of Stellar evolution The S-process or slow-neutron -capture-process is a Nucleosynthesis process that occurs at relatively low neutron density and intermediate temperature conditions in [105] Elements such as lead formed largely through the radioactive decay of heavier elements. Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly [106]

### Earth

There are a few trace atoms on Earth that were not present at the beginning (i. e. , not "primordial"), nor are results of radioactive decay. Carbon-14 is continuously generated by cosmic rays in the atmosphere. Carbon-14, 14C, or radiocarbon, is a Radioactive isotope of Carbon discovered on February 27, 1940, by [110] Some atoms on Earth have been artificially generated either deliberately or as by-products of nuclear reactors or explosions. [111][112] Of the transuranic elements—those with atomic numbers greater than 92—only plutonium and neptunium occur naturally on Earth. In Chemistry, transuranium elements (also known as transuranic elements) are the Chemical elements with Atomic numbers greater than 92 (the atomic Neptunium (nɛpˈtjuːniəm is a Chemical element with the symbol Np and Atomic number 93 [113][114] Transuranic elements have radioactive lifetimes shorter than the current age of the Earth[115] and thus identifiable quantities of these elements have long since decayed, with the exception of traces of plutonium-244 possibly deposited by cosmic dust. See also Isotopes of plutonium Plutonium -244 has a Halflife of 80 million years [107] Natural deposits of plutonium and neptunium are produced by neutron capture in uranium ore. Neutron capture is a kind of Nuclear reaction in which an Atomic nucleus collides with one or more Neutrons and they merge to form a heavier nucleus [116]

The Earth contains approximately 1. 33×1050 atoms. [117] In the planet's atmosphere, small numbers of independent atoms exist for the noble gases, such as argon and neon. History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity This article pertains to the chemical element For other uses see Argon (disambiguation. Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 The remaining 99% of the atmosphere is bound in the form of molecules, including carbon dioxide and diatomic oxygen and nitrogen. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Diatomic molecules are molecules made only of two Atoms of either the same or different Chemical elements The prefix di- means two in Greek Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 At the surface of the Earth, atoms combine to form various compounds, including water, salt, silicates and oxides. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants For the Artificial intelligence Androids of the 1990s Science fiction series Space Above and Beyond, see Silicate (AI An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element Atoms can also combine to create materials that do not consist of discrete molecules, including crystals and liquid or solid metals. In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across [118][119] This atomic matter forms networked arrangements that lack the particular type of small-scale interrupted order associated with molecular matter. [120]

### Rare and theoretical forms

While isotopes with atomic numbers higher than lead (82) are known to be radioactive, an "island of stability" has been proposed for some elements with atomic numbers above 103. Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly The island of stability is a term from Nuclear physics that describes the possibility of elements with particularly stable " magic numbers " These superheavy elements may have a nucleus that is relatively stable against radioactive decay. In Chemistry, transuranium elements (also known as transuranic elements) are the Chemical elements with Atomic numbers greater than 92 (the atomic [121] The most likely candidate for a stable superheavy atom, unbihexium, has 126 protons and 184 neutrons. [122]

Each particle of matter has a corresponding antimatter particle with the opposite electrical charge. In Particle physics and Quantum chemistry, antimatter is the extension of the concept of the Antiparticle to Matter, where antimatter is composed Thus, the positron is a positively charged antielectron and the antiproton is a negatively charged equivalent of a proton. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. For unknown reasons, antimatter particles are rare in the universe, hence, no antimatter atoms have been discovered. [123][124] Antihydrogen, the antimatter counterpart of hydrogen, was first produced at the CERN laboratory in Geneva in 1996. Antihydrogen is the Antimatter counterpart of Hydrogen. Whereas the common hydrogen Atom is composed of an Electron and Proton The European Organization for Nuclear Research (Organisation Européenne pour la Recherche Nucléaire known as CERN Geneva (Genève is the second-most populous city in Switzerland (after Zürich) and is the most populous city of Romandy (the French -speaking [125][126]

Other exotic atoms have been created by replacing one of the protons, neutrons or electrons with other particles that have the same charge. An exotic atom is a normal Atom in which one or more sub-atomic particles have been replaced by other particles of the same charge For example, an electron can be replaced by a more massive muon, forming a muonic atom. The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 An exotic atom is a normal Atom in which one or more sub-atomic particles have been replaced by other particles of the same charge These types of atoms can be used to test the fundamental predictions of physics. [127][128][129]

## References

### Notes

1. ^ Haubold, Hans; Mathai, A. Quantum mechanics (QM or quantum theory) is a physical science dealing with the behavior of Matter and Energy on the scale of Atoms The history of Quantum mechanics as this interlaces with history of Quantum chemistry began essentially with the 1838 discovery of Cathode rays The concept of infinite divisibility arises in different ways in Philosophy, Physics, Economics, Order theory (a branch of mathematics and This is a list of the different types of particles known and hypothesized A nuclear model is any model that attempts to describe the Atomic nucleus. A radionuclide is an Atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created In Chemistry, transuranium elements (also known as transuranic elements) are the Chemical elements with Atomic numbers greater than 92 (the atomic M. (1998). Microcosmos: From Leucippus to Yukawa. Structure of the Universe. Common Sense Science. Retrieved on 2008-01-17. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 38 BC - Octavian marries Livia Drusilla. 1287 - King Alfonso III of Aragon invades Minorca
2. ^ Harrison (2003:123–139).
3. ^ Most isotopes have more nucleons than electrons. In the corner case of hydrogen-1, with a single electron and nucleon, the proton is $\begin{smallmatrix}\frac{1836}{1837} \approx 0.9995\end{smallmatrix}$, or 99. 95% of the total atomic mass.
4. ^ Staff (August 1, 2007). Events 30 BC - Octavian (later known as Augustus enters Alexandria, Egypt, bringing it under the control of the Roman Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Radioactive Decays. Stanford Linear Accelerator Center, Stanford University. Retrieved on 2007-01-02. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 366 - The Alamanni cross the frozen Rhine River in large numbers invading the Roman Empire.
5. ^ a b Ponomarev (1993:14–15).
7. ^ Teresi (2003:213–214).
8. ^ Siegfried (2002:42–55).
9. ^ Lavoisier's Elements of Chemistry. Elements and Atoms. Le Moyne College, Department of Chemistry. Retrieved on 2007-12-18. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 218 BC - Second Punic War: Battle of the Trebia - Hannibal 's Carthaginian forces defeat those of the
10. ^ Wurtz (1881:1–2).
11. ^ Dalton (1808).
12. ^ Mazo (2002:1–7).
13. ^ Lee, Y. K. ; Hoon, Kelvin (1995). Brownian Motion. Imperial College, London. Retrieved on 2007-12-18. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 218 BC - Second Punic War: Battle of the Trebia - Hannibal 's Carthaginian forces defeat those of the
14. ^ The Nobel Foundation (1906). J.J. Thomson. Nobelprize. org. Retrieved on 2007-12-20. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 69 - Vespasian, formerly a general under Nero, enters Rome to claim the title of Emperor.
15. ^ Rutherford, E. (1911). "The Scattering of α and β Particles by Matter and the Structure of the Atom". Philosophical Magazine 21: 669–88.
16. ^ Frederick Soddy, The Nobel Prize in Chemistry 1921. Nobel Foundation. Retrieved on 2008-01-18. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 350 - Generallus Magnentius deposes Roman Emperor Constans and proclaims himself Emperor
17. ^ Thomson, Joseph John (1913). "Rays of positive electricity". Proceedings of the Royal Society A 89: 1–20.
18. ^ Stern, David P. (May 16, 2005). Events 1204 - Baldwin IX Count of Flanders is crowned as the first Emperor of the Latin Empire. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. The Atomic Nucleus and Bohr's Early Model of the Atom. NASA Goddard Space Flight Center. Retrieved on 2007-12-20. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 69 - Vespasian, formerly a general under Nero, enters Rome to claim the title of Emperor.
19. ^ Bohr, Niels (December 11, 1922). Events 359 - Honoratus, the first known Prefect of the City of Constantinople, takes office Year 1922 ( MCMXXII) was a Common year starting on Sunday of the Gregorian calendar. Niels Bohr, The Nobel Prize in Physics 1922, Nobel Lecture. The Nobel Foundation. Retrieved on 2008-02-16. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1249 - Andrew of Longjumeau is dispatched by Louis IX of France as his ambassador to meet with the Khan of the Mongols
20. ^ Brown, Kevin (2007). The Hydrogen Atom. MathPages. Retrieved on 2007-12-21. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 69 - The end of the Year of the four emperors: Following Galba, Otho and Vitellius, Vespasian
21. ^ Harrison, David M. (March 2000). The Development of Quantum Mechanics. University of Toronto. Retrieved on 2007-12-21. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 69 - The end of the Year of the four emperors: Following Galba, Otho and Vitellius, Vespasian
22. ^ Aston, Francis W. (1920). "The constitution of atmospheric neon". Philosophical Magazine 39 (6): 449–55.
23. ^ Chadwick, James (December 12, 1935). Events 627 - Battle of Nineveh: A Byzantine army under Emperor Heraclius defeats Emperor Khosrau II 's Persian Year 1935 ( MCMXXXV) was a Common year starting on Tuesday (link will display full calendar of the Gregorian calendar. Nobel Lecture: The Neutron and Its Properties. Nobel Foundation. Retrieved on 2007-12-21. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 69 - The end of the Year of the four emperors: Following Galba, Otho and Vitellius, Vespasian
24. ^ Kullander, Sven (August 28, 2001). Events 475 - The Roman General Orestes forces western Roman Emperor Julius Nepos to flee his Capital Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Accelerators and Nobel Laureates. The Nobel Foundation. Retrieved on 2008-01-31. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1504 - France cedes Naples to Aragon. 1606 - Gunpowder Plot: Guy Fawkes
25. ^ Staff (October 17, 1990). Events 539 BC - King Cyrus The Great of Persia marches into the city of Babylon, releasing the Jews from almost Year 1990 ( MCMXC) was a Common year starting on Monday (link displays the 1990 Gregorian calendar) The Nobel Prize in Physics 1990. The Nobel Foundation. Retrieved on 2008-01-31. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1504 - France cedes Naples to Aragon. 1606 - Gunpowder Plot: Guy Fawkes
26. ^ Staff (October 15, 1997). Events 533 - Byzantine General Belisarius makes his formal entry into Carthage, having conquered it from the Year 1997 ( MCMXCVII) was a Common year starting on Wednesday (link will display full 1997 Gregorian calendar The Nobel Prize in Physics 1997. Nobel Foundation. Retrieved on 2008-02-10. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1355 - The St Scholastica's Day riot breaks out in Oxford, England, leaving 63 scholars and perhaps 30 locals dead
27. ^ Park, Jiwoong et al (2002). "Coulomb blockade and the Kondo effect in single-atom transistors". Nature 417 (6890): 722–25. doi:10.1038/nature00791. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
28. ^ Domokos, P. ; Janszky, J. ; Adam, P. (1994). "Single-atom interference method for generating Fock states". Physical Review A 50: 3340–44. doi:10.1103/PhysRevA.50.3340. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
29. ^ Demtröder (2002:39–42).
30. ^ Woan (2000:8).
31. ^ MacGregor (1992:33–37).
32. ^ Particle Data Group (2002). The Particle Adventure. Lawrence Berkeley Laboratory. Retrieved on 2007-01-03. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1431 - Joan of Arc is handed over to the Bishop Pierre Cauchon.
33. ^ Schombert, James (April 18, 2006). Events 1025 - Bolesław Chrobry is crowned in Gniezno, becoming the first King of Poland. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Elementary Particles. University of Oregon. Retrieved on 2007-01-03. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1431 - Joan of Arc is handed over to the Bishop Pierre Cauchon.
34. ^ Jevremovic (2005:63).
35. ^ Pfeffer (2000:330–336).
36. ^ Wenner, Jennifer M. (October 10, 2007). Events 680 - Battle of Karbala: Shia Imam Husayn bin Ali, the grandson of the Prophet Muhammad, is decapitated Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. How Does Radioactive Decay Work?. Carleton College. Retrieved on 2008-01-09. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 475 - Byzantine Emperor Zeno is forced to flee his capital at Constantinople.
37. ^ a b c Raymond, David (April 7, 2006). Events 529 - First draft of Corpus Juris Civilis (a fundamental work in Jurisprudence) is issued by Eastern Roman Emperor Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Nuclear Binding Energies. New Mexico Tech. Retrieved on 2007-01-03. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1431 - Joan of Arc is handed over to the Bishop Pierre Cauchon.
38. ^ Mihos, Chris (July 23, 2002). Events 1632 - Three hundred colonists bound for New France depart from Dieppe France. See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar. Overcoming the Coulomb Barrier. Case Western Reserve University. Retrieved on 2008-02-13. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1258 - Baghdad falls to the Mongols, and the Abbasid Caliphate is destroyed
39. ^ Staff (March 30, 2007). Events 240 BC - 1st recorded Perihelion passage of Halley's Comet. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. ABC's of Nuclear Science. Lawrence Berkeley National Laboratory. Retrieved on 2007-01-03. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1431 - Joan of Arc is handed over to the Bishop Pierre Cauchon.
40. ^ Makhijani, Arjun; Saleska, Scott (March 2, 2001). Events 986 - Louis V becomes King of the Franks. 1127 - Assassination of Charles the Good Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Basics of Nuclear Physics and Fission. Institute for Energy and Environmental Research. Retrieved on 2007-01-03. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1431 - Joan of Arc is handed over to the Bishop Pierre Cauchon.
41. ^ Shultis et al (2002:72–6).
42. ^ Fewell, M. P. (1995). "The atomic nuclide with the highest mean binding energy". American Journal of Physics 63 (7): 653–58. The American Journal of Physics is a Peer-reviewed Scientific journal published by the American Association of Physics Teachers devoted to the educational doi:10.1119/1.17828. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
43. ^ a b Brucat, Philip J. (2008). The Quantum Atom. University of Florida. Retrieved on 2007-01-04. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 46 BC - Titus Labienus defeats Julius Caesar in the Battle of Ruspina.
44. ^ Manthey, David (2001). Atomic Orbitals. Orbital Central. Retrieved on 2008-01-21. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1189 - Philip II of France and Richard I of England begin to assemble troops to wage the Third Crusade.
45. ^ Herter, Terry (2006). Lecture 8: The Hydrogen Atom. Cornell University. Retrieved on 2008-02-14. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 842 - Charles the Bald and Louis the German swear the Oaths of Strasbourg in the French and German
46. ^ Smirnov (2003:249–72).
47. ^ Matis, Howard S. (August 9, 2000). Events 48 BC - Caesar's civil war: Battle of Pharsalus - Julius Caesar decisively defeats Pompey at Pharsalus 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. The Isotopes of Hydrogen. Guide to the Nuclear Wall Chart. Lawrence Berkeley National Lab. Retrieved on 2007-12-21. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 69 - The end of the Year of the four emperors: Following Galba, Otho and Vitellius, Vespasian
48. ^ Weiss, Rick. "Scientists Announce Creation of Atomic Element, the Heaviest Yet", Washington Post, October 17, 2006. Events 539 BC - King Cyrus The Great of Persia marches into the city of Babylon, releasing the Jews from almost Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Retrieved on 2007-12-21. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 69 - The end of the Year of the four emperors: Following Galba, Otho and Vitellius, Vespasian
49. ^ a b Sills (2003:131–134).
50. ^ Dumé, Belle. "Bismuth breaks half-life record for alpha decay", Physics World, April 23, 2003. Events 215 BC - A temple is built on the Capitoline Hill dedicated to Venus Erycina to commemorate the Roman defeat at Year 2003 ( MMIII) was a Common year starting on Wednesday of the Gregorian calendar. Retrieved on 2007-12-21. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 69 - The end of the Year of the four emperors: Following Galba, Otho and Vitellius, Vespasian
51. ^ Lindsay, Don (July 30, 2000). Events 1419 - First Defenestration of Prague. 1502 - Christopher Columbus lands at Guanaja in the Bay Islands off 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Radioactives Missing From The Earth. Don Lindsay Archive. Retrieved on 2007-05-23. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1430 - Siege of Compiègne: Joan of Arc is captured by the Burgundians while leading an army to relieve Compiègne
52. ^ a b CRC Handbook (2002).
53. ^ a b Mills et al (1993).
54. ^ Chieh, Chung (January 22, 2001). Events 565 - Eutychius is deposed as Patriarch of Constantinople by John Scholasticus. Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Nuclide Stability. University of Waterloo. Retrieved on 2007-01-04. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 46 BC - Titus Labienus defeats Julius Caesar in the Battle of Ruspina.
55. ^ Atomic Weights and Isotopic Compositions for All Elements. National Institute of Standards and Technology. Retrieved on 2007-01-04. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 46 BC - Titus Labienus defeats Julius Caesar in the Battle of Ruspina.
56. ^ Audi, G. ; Wapstra, A. H. ; Thibault C. (2003). "The Ame2003 atomic mass evaluation (II)". Nuclear Physics A729: 337–676.
57. ^ Shannon, R. D. (1976). "Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides". Acta Crystallographica, Section A 32: 751. doi:10.1107/S0567739476001551. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
58. ^ Dong, Judy (1998). Diameter of an Atom. The Physics Factbook. Retrieved on 2007-11-19. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1095 - The Council of Clermont, called by Pope Urban II to discuss sending the First Crusade to the Holy Land
59. ^ Zumdahl (2002).
60. ^ Staff (2007). Small Miracles: Harnessing nanotechnology. Oregon State University. Retrieved on 2007-01-07. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1325 - Alfonso IV becomes King of Portugal. 1558 - France takes Calais, the last continental —describes the width of a human hair as 105 nm and 10 carbon atoms as spanning 1 nm.
61. ^ Padilla et al (2002:32)—"There are 2,000,000,000,000,000,000,000 (that's 2 sextillion) atoms of oxygen in one drop of water—and twice as many atoms of hydrogen. "
62. ^ A carat is 200 milligrams. By definition, Carbon-12 has 12 grams per mole. The atomic mass (ma is the Mass of an atom most often expressed in unified atomic mass units The atomic mass may be considered to be the total mass The Avogadro constant defines 6×1023 atoms per mole. The Avogadro constant (symbols L, N A also called Avogadro's number, is the number of "elementary entities" (usually Atoms
63. ^ Feynman (1995).
64. ^ a b Radioactivity. Splung. com. Retrieved on 2007-12-19. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 324 - Licinius abdicates his position as Roman Emperor.
65. ^ L'Annunziata (2003:3–56).
66. ^ Firestone, Richard B. (May 22, 2000). Events 334 BC - The Greek army of Alexander the Great defeats Darius III of Persia in the Battle of the Granicus. 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Radioactive Decay Modes. Berkeley Laboratory. Retrieved on 2007-01-07. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1325 - Alfonso IV becomes King of Portugal. 1558 - France takes Calais, the last continental
67. ^ Hornak, J. P. (2006). Chapter 3: Spin Physics. The Basics of NMR. Rochester Institute of Technology. Retrieved on 2007-01-07. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1325 - Alfonso IV becomes King of Portugal. 1558 - France takes Calais, the last continental
68. ^ a b Schroeder, Paul A. (February 25, 2000). Events 138 - The Emperor Hadrian adopts Antoninus Pius, effectively making him his successor 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Magnetic Properties. University of Georgia. Retrieved on 2007-01-07. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1325 - Alfonso IV becomes King of Portugal. 1558 - France takes Calais, the last continental
69. ^ Goebel, Greg (September 1, 2007). Events 462 - Possible start of first Byzantine indiction cycle. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. [4.3] Magnetic Properties of the Atom. Elementary Quantum Physics. In The Public Domain website. Retrieved on 2007-01-07. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1325 - Alfonso IV becomes King of Portugal. 1558 - France takes Calais, the last continental
70. ^ Yarris, Lynn (Spring 1997). "Talking Pictures". Berkeley Lab Research Review.
71. ^ Liang and Haacke (1999:412–26).
72. ^ Zeghbroeck, Bart J. Van (1998). Energy levels. Shippensburg University. Retrieved on 2007-12-23. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 962 - Byzantine-Arab Wars: Under the future Emperor Nicephorus Phocas, Byzantine troops stormed the city
73. ^ Fowles (1989:227–233).
74. ^ Martin, W. C. ; Wiese, W. L. (May 2007). Atomic Spectroscopy: A Compendium of Basic Ideas, Notation, Data, and Formulas. National Institute of Standards and Technology. Retrieved on 2007-01-08. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 871 - Battle of Ashdown - Ethelred of Wessex defeats a Danish invasion army
75. ^ Atomic Emission Spectra - Origin of Spectral Lines. Avogadro Web Site. Retrieved on 2006-08-10. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 612 BC - Killing of Sinsharishkun, King of Assyrian Empire
76. ^ Fitzpatrick, Richard (February 16, 2007). Events 1249 - Andrew of Longjumeau is dispatched by Louis IX of France as his ambassador to meet with the Khan of the Mongols Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Fine structure. University of Texas at Austin. Retrieved on 2008-02-14. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 842 - Charles the Bald and Louis the German swear the Oaths of Strasbourg in the French and German
77. ^ Weiss, Michael (2001). The Zeeman Effect. University of California-Riverside. Retrieved on 2008-02-06. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 46 BC - Julius Caesar defeats the combined army of Pompeian followers and Numidians under Metellus Scipio
78. ^ Beyer (2003:232–236).
79. ^ Watkins, Thayer. Coherence in Stimulated Emission. San José State University. Retrieved on 2007-12-23. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 962 - Byzantine-Arab Wars: Under the future Emperor Nicephorus Phocas, Byzantine troops stormed the city
80. ^ Reusch, William (July 16, 2007). Events 622 - The beginning of the Islamic calendar. 1054 - Three Roman legates fractured relations between the Western and Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Virtual Textbook of Organic Chemistry. Michigan State University. Retrieved on 2008-01-11. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1055 - Theodora is crowned Empress of the Byzantine Empire.
81. ^ Husted, Robert et al (December 11, 2003). Events 359 - Honoratus, the first known Prefect of the City of Constantinople, takes office Year 2003 ( MMIII) was a Common year starting on Wednesday of the Gregorian calendar. Periodic Table of the Elements. Los Alamos National Laboratory. Retrieved on 2008-01-11. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1055 - Theodora is crowned Empress of the Byzantine Empire.
82. ^ Baum, Rudy (2003). It's Elemental: The Periodic Table. Chemical & Engineering News. Retrieved on 2008-01-11. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1055 - Theodora is crowned Empress of the Byzantine Empire.
83. ^ Goodstein (2002:436–438).
84. ^ Brazhkin, Vadim V. (2006). "Metastable phases, phase transformations, and phase diagrams in physics and chemistry". Physics-Uspekhi 49: 719–24. doi:10.1070/PU2006v049n07ABEH006013. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
85. ^ Myers (2003:85).
86. ^ Staff. "Bose-Einstein Condensate: A New Form of Matter", National Institute of Standards and Technology, October 9, 2001. Events 768 - Carloman I and Charlemagne are crowned Kings of The Franks. Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Retrieved on 2008-01-16. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 27 BC - The title Augustus is bestowed upon Gaius Julius Caesar Octavian by the Roman Senate.
87. ^ Colton, Imogen; Fyffe, Jeanette (February 3, 1999). Events 1112 - Ramon Berenguer III of Barcelona and Douce I of Provence marry uniting the fortunes of those two states Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Super Atoms from Bose-Einstein Condensation. The University of Melbourne. Retrieved on 2008-02-06. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 46 BC - Julius Caesar defeats the combined army of Pompeian followers and Numidians under Metellus Scipio
88. ^ Jacox, Marilyn; Gadzuk, J. William (November 1997). Scanning Tunneling Microscope. National Institute of Standards and Technology. Retrieved on 2008-01-11. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1055 - Theodora is crowned Empress of the Byzantine Empire.
89. ^ The Nobel Prize in Physics 1986. The Nobel Foundation. Retrieved on 2008-01-11. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1055 - Theodora is crowned Empress of the Byzantine Empire. —in particular, see the Nobel lecture by G. Binnig and H. Rohrer.
90. ^ Jakubowski, N. ; Moens, L. ; Vanhaecke, F (1998). "Sector field mass spectrometers in ICP-MS". Spectrochimica Acta Part B: Atomic Spectroscopy 53 (13): 1739–63. doi:10.1016/S0584-8547(98)00222-5. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
91. ^ Müller, Erwin W.; Panitz, John A., McLane, S. Erwin Müller may refer to Erwin Wilhelm Müller (1911–1977 German physicist Erwin Franz Müller (born 1932 founder of Müller J A Panitz is the co-inventor of the Atom-Probe Field Ion Microscope and the inventor of the 10-cm atom-probe which was the precursor of his Imaging Atom-Probe mass spectrometer Brooks (1968). "The Atom-Probe Field Ion Microscope". Review of Scientific Instruments 39 (1): 83–86. doi:10.1063/1.1683116. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. ISSN 0034-6748. An International Standard Serial Number ( ISSN) is a unique eight-digit number used to identify a print or electronic Periodical publication.
92. ^ Lochner, Jim; Gibb, Meredith; Newman, Phil (April 30, 2007). Events 313 - Roman emperor Licinius unifies the entire Eastern Roman Empire under his rule Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. What Do Spectra Tell Us?. NASA/Goddard Space Flight Center. Retrieved on 2008-01-03. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1431 - Joan of Arc is handed over to the Bishop Pierre Cauchon.
93. ^ Winter, Mark (2007). Helium. WebElements. Retrieved on 2008-01-03. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1431 - Joan of Arc is handed over to the Bishop Pierre Cauchon.
94. ^ Hinshaw, Gary (February 10, 2006). Events 1355 - The St Scholastica's Day riot breaks out in Oxford, England, leaving 63 scholars and perhaps 30 locals dead Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. What is the Universe Made Of?. NASA/WMAP. Retrieved on 2008-01-07. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1325 - Alfonso IV becomes King of Portugal. 1558 - France takes Calais, the last continental
95. ^ Choppin et al (2001).
96. ^ Davidsen, Arthur F. (1993). "Far-Ultraviolet Astronomy on the Astro-1 Space Shuttle Mission". Science 259 (5093): 327–34. doi:10.1126/science.259.5093.327. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17832344.
97. ^ Lequeux (2005).
98. ^ Smith, Nigel (January 6, 2000). Events 1066 - Harold Godwinson is crowned King of England. 1205 - Philip of Swabia becomes King 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. The search for dark matter. Physics World. Retrieved on 2008-02-14. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 842 - Charles the Bald and Louis the German swear the Oaths of Strasbourg in the French and German
99. ^ Croswell, Ken (1991). "Boron, bumps and the Big Bang: Was matter spread evenly when the Universe began? Perhaps not; the clues lie in the creation of the lighter elements such as boron and beryllium". New Scientist (1794): 42.
100. ^ Copi, Craig J. ; Schramm, David N. ; Turner, Michael S (1995). "Big-Bang Nucleosynthesis and the Baryon Density of the Universe" (PDF). Science 267: 192–99. doi:10.1126/science.7809624. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 7809624.
101. ^ Hinshaw, Gary (December 15, 2005). Events 533 - Byzantine general Belisarius defeats the Vandals, commanded by King Gelimer, at the Battle of Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Tests of the Big Bang: The Light Elements. NASA/WMAP. Retrieved on 2008-01-13. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 532 - Nika riots in Constantinople. 888 - Odo Count of Paris becomes King of the Franks
102. ^ Abbott, Brian (May 30, 2007). Events 1416 - The Council of Constance, called by the Emperor Sigismund a supporter of Antipope John XXIII burns Jerome of Prague following Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Microwave (WMAP) All-Sky Survey. Hayden Planetarium. Retrieved on 2008-01-13. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 532 - Nika riots in Constantinople. 888 - Odo Count of Paris becomes King of the Franks
103. ^ F. Hoyle (1946). "The synthesis of the elements from hydrogen". Monthly Notices of the Royal Astronomical Society 106: 343–83. Monthly Notices of the Royal Astronomical Society (MNRAS is one of the world's leading Scientific journals in Astronomy and Astrophysics.
104. ^ Knauth, D. C. ; Federman, S. R. ; Lambert, David L. ; Crane, P. (2000). "Newly synthesized lithium in the interstellar medium". Nature 405: 656–58. doi:10.1038/35015028. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
105. ^ Mashnik, Stepan G. (August 2000). On Solar System and Cosmic Rays Nucleosynthesis and Spallation Processes. Cornell University. Retrieved on 2008-01-14. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1129 - Formal approval of the Order of the Templar at the Council of Troyes.
106. ^ Kansas Geological Survey (May 4, 2005). Events 1256 - The Augustinian monastic order is constituted at the Lecceto Monastery when Pope Alexander IV Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Age of the Earth. University of Kansas. Retrieved on 2008-01-14. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1129 - Formal approval of the Order of the Templar at the Council of Troyes.
107. ^ a b Manuel (2001).
108. ^ Dalrymple, G. Brent (2001). "The age of the Earth in the twentieth century: a problem (mostly) solved". Geological Society, London, Special Publications 190: 205–21. doi:10.1144/GSL.SP.2001.190.01.14. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
109. ^ Anderson, Don L.; Foulger, G. Don L Anderson (* 5 March, 1933, in Frederick, Maryland, USA is a US geophysicist who has made important contributions to the determination R. ; Meibom, Anders (September 2, 2006). Events 44 BC - Pharaoh Cleopatra VII of Egypt declares her son co-ruler as Ptolemy XV Caesarion. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Helium: Fundamental models. MantlePlumes. org. Retrieved on 2007-01-14. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1129 - Formal approval of the Order of the Templar at the Council of Troyes.
110. ^ Pennicott, Katie. "Carbon clock could show the wrong time", PhysicsWeb, May 10, 2001. Events 1291 - Scottish Nobles recognize the authority of Edward I of England. Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Retrieved on 2008-01-14. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1129 - Formal approval of the Order of the Templar at the Council of Troyes.
111. ^ Yarris, Lynn. "New Superheavy Elements 118 and 116 Discovered at Berkeley Lab", Berkeley Lab, July 27, 2001. Events 1214 - Battle of Bouvines: In France, Philip II of France defeats John of England. Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Retrieved on 2008-01-14. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1129 - Formal approval of the Order of the Templar at the Council of Troyes.
112. ^ Diamond, H. et al (1960). "Heavy Isotope Abundances in Mike Thermonuclear Device" (subscription required). Physical Review 119: 2000–04. doi:10.1103/PhysRev.119.2000. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
113. ^ Poston Sr. , John W. (March 23, 1998). Events 1174 - Jocelin, Abbot of Melrose, is elected Bishop of Glasgow. Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) Do transuranic elements such as plutonium ever occur naturally?. Scientific American. Retrieved on 2008-01-15. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 588 BC - Nebuchadrezzar II of Babylon lays siege to Jerusalem under Zedekiah 's reign
114. ^ Keller, C. (1973). "Natural occurrence of lanthanides, actinides, and superheavy elements". Chemiker Zeitung 97 (10): 522–30.
115. ^ Marco (2001).
116. ^ Oklo Fossil Reactors. Curtin University of Technology. Retrieved on 2008-01-15. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 588 BC - Nebuchadrezzar II of Babylon lays siege to Jerusalem under Zedekiah 's reign
117. ^ Weisenberger, Drew. How many atoms are there in the world?. Jefferson Lab. Retrieved on 2008-01-16. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 27 BC - The title Augustus is bestowed upon Gaius Julius Caesar Octavian by the Roman Senate.
118. ^ Pidwirny, Michael. Fundamentals of Physical Geography. University of British Columbia Okanagan. Retrieved on 2008-01-16. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 27 BC - The title Augustus is bestowed upon Gaius Julius Caesar Octavian by the Roman Senate.
119. ^ Anderson, Don L. (2002). "The inner inner core of Earth". Proceedings of the National Academy of Science 99 (22): 13966–68. doi:10.1073/pnas.232565899. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 12391308.
120. ^ Pauling (1960).
121. ^ Anonymous (October 2, 2001). Events 1187 - Siege of Jerusalem: Saladin captures Jerusalem after 88 years of Crusader rule Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. "Second postcard from the island of stability". CERN Courier.
122. ^ Jacoby, Mitch (2006). "As-yet-unsynthesized superheavy atom should form a stable diatomic molecule with fluorine". Chemical & Engineering News 84 (10): 19.
123. ^ Koppes, Steve. "Fermilab Physicists Find New Matter-Antimatter Asymmetry", University of Chicago, March 1, 1999. Events 86 BC - Lucius Cornelius Sulla, at the head of a Roman Republic army enters in Athens, removing the Tyrant Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Retrieved on 2008-01-14. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1129 - Formal approval of the Order of the Templar at the Council of Troyes.
124. ^ Cromie, William J. . "A lifetime of trillionths of a second: Scientists explore antimatter", Harvard University Gazette, August 16, 2001. Events 1384 - The Hongwu Emperor of Ming China, Emperor Dong hears a case of a couple who tore paper money bills while fighting Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Retrieved on 2008-01-14. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1129 - Formal approval of the Order of the Templar at the Council of Troyes.
125. ^ Hijmans, Tom W. (2002). "Particle physics: Cold antihydrogen". Nature 419: 439–40. doi:10.1038/419439a. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
126. ^ Staff. "Researchers 'look inside' antimatter", BBC News, October 30, 2002. Events 637 - Antioch surrenders to the Muslim forces under Rashidun Caliphate after the Battle of Iron bridge. See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar. Retrieved on 2008-01-14. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1129 - Formal approval of the Order of the Templar at the Council of Troyes.
127. ^ Barrett, Roger; Jackson, Daphne; Mweene, Habatwa (1990). "The Strange World of the Exotic Atom". New Scientist (1728): 77–115.
128. ^ Indelicato, Paul (2004). "Exotic Atoms". Physica Scripta T112: 20–26. doi:10.1238/Physica.Topical.112a00020. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
129. ^ Ripin, Barrett H. (July 1998). Recent Experiments on Exotic Atoms. American Physical Society. Retrieved on 2008-02-15. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 590 - Khosrau II is crowned as king of Persia 1637 - Ferdinand III becomes Holy Roman Emperor

### Book references

• L'Annunziata, Michael F. (2003). Handbook of Radioactivity Analysis. Academic Press. ISBN 0124366031.
• Beyer, H. F. ; Shevelko, V. P. (2003). Introduction to the Physics of Highly Charged Ions. CRC Press. ISBN 0750304812.
• Choppin, Gregory R. ; Liljenzin, Jan-Olov; Rydberg, Jan (2001). Radiochemistry and Nuclear Chemistry. Elsevier. ISBN 0750674636.
• Dalton, J. (1808). John Dalton FRS (6 September 1766 &ndash 27 July 1844 was an English Chemist, Meteorologist and Physicist. A New System of Chemical Philosophy, Part 1. London and Manchester: S. Russell.
• Demtröder, Wolfgang (2002). Atoms, Molecules and Photons: An Introduction to Atomic- Molecular- and Quantum Physics, 1st Edition, Springer. ISBN 3540206310.
• Feynman, Richard (1995). Six Easy Pieces. The Penguin Group. ISBN 978-0-140-27666-4.
• Fowles, Grant R. (1989). Introduction to Modern Optics. Courier Dover Publications. ISBN 0486659577.
• Gangopadhyaya, Mrinalkanti (1981). Indian Atomism: History and Sources. Atlantic Highlands, New Jersey: Humanities Press. ISBN 0-391-02177-X.
• Goodstein, David L. (2002). States of Matter. Courier Dover Publications. ISBN 048649506X.
• Harrison, Edward Robert (2003). Masks of the Universe: Changing Ideas on the Nature of the Cosmos. Cambridge University Press. ISBN 0521773512.
• Jevremovic, Tatjana (2005). Nuclear Principles in Engineering. Springer. ISBN 0387232842.
• Lequeux, James (2005). The Interstellar Medium. Springer. ISBN 3540213260.
• Liang, Z. -P. ; Haacke, E. M. (1999). in Webster, J. G. : Encyclopedia of Electrical and Electronics Engineering: Magnetic Resonance Imaging (PDF) vol. 2, John Wiley & Sons, pp. 412–26. ISBN 0471139467. Retrieved on 2008-01-09. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 475 - Byzantine Emperor Zeno is forced to flee his capital at Constantinople.
• MacGregor, Malcolm H. (1992). The Enigmatic Electron. Oxford University Press. ISBN 0195218337.
• Manuel, Oliver (2001). Origin of Elements in the Solar System: Implications of Post-1957 Observations. Springer. ISBN 0306465620.
• Mazo, Robert M. (2002). Brownian Motion: Fluctuations, Dynamics, and Applications. Oxford University Press. ISBN 0198515677.
• Mills, Ian; Cvitaš, Tomislav; Homann, Klaus; Kallay, Nikola; Kuchitsu, Kozo (1993). Quantities, Units and Symbols in Physical Chemistry, 2nd edition, Oxford: International Union of Pure and Applied Chemistry, Commission on Physiochemical Symbols Terminology and Units, Blackwell Scientific Publications. The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization ISBN 0-632-03583-8.
• Myers, Richard (2003). The Basics of Chemistry. Greenwood Press. ISBN 0313316643.
• Padilla, Michael J. ; Miaoulis, Ioannis; Cyr, Martha (2002). Prentice Hall Science Explorer: Chemical Building Blocks. Upper Saddle River, New Jersey USA: Prentice-Hall, Inc. . ISBN 0-13-054091-9.
• Pauling, Linus (1960). The Nature of the Chemical Bond. Cornell University Press. ISBN 0801403332.
• Pfeffer, Jeremy I. (2000). Modern Physics: An Introductory Text. Imperial College Press. ISBN 1860942504.
• Ponomarev, Leonid Ivanovich (1993). The Quantum Dice. CRC Press. ISBN 0750302518.
• Shultis, J. Kenneth; Faw, Richard E. (2002). Fundamentals of Nuclear Science and Engineering. CRC Press. ISBN 0824708342.
• Siegfried, Robert (2002). From Elements to Atoms: A History of Chemical Composition. DIANE. ISBN 0871699249.
• Sills, Alan D. (2003). Earth Science the Easy Way. Barron's Educational Series. ISBN 0764121464.
• Smirnov, Boris M. (2003). Physics of Atoms and Ions. Springer. ISBN 038795550X.
• Teresi, Dick (2003). Lost Discoveries: The Ancient Roots of Modern Science. Simon & Schuster, 213–214. ISBN 074324379X.
• Various (2002). in Lide, David R. : Handbook of Chemistry & Physics, 88th edition, CRC. ISBN 0849304865. Retrieved on 2008-05-23. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1430 - Siege of Compiègne: Joan of Arc is captured by the Burgundians while leading an army to relieve Compiègne
• Woan, Graham (2000). The Cambridge Handbook of Physics. Cambridge University Press. ISBN 0521575079.
• Wurtz, Charles Adolphe (1881). The Atomic Theory. New York: D. Appleton and company.
• Zaider, Marco; Rossi, Harald H. (2001). Radiation Science for Physicians and Public Health Workers. Springer. ISBN 0306464039.
• Zumdahl, Steven S. (2002). Introductory Chemistry: A Foundation, 5th edition, Houghton Mifflin. ISBN 0-618-34342-3. Retrieved on 2008-02-05. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1576 - Henry of Navarre converts to Roman Catholicism in order to ensure his right to the throne of France.