Nuclear physics

Radioactive decay Nuclear fission Nuclear fusion

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Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. Nuclear physics is the field of Physics that studies the building blocks and interactions of Atomic nuclei. 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 In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy Particle radiation is the radiation of Energy by means of fast-moving Subatomic particles. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies This decay, or loss of energy, results in an atom of one type, called the parent nuclide transforming to an atom of a different type, called the daughter nuclide. For example: a carbon-14 atom (the "parent") emits radiation and transforms to a nitrogen-14 atom (the "daughter"). This is a random process on the atomic level, in that it is impossible to predict when a particular atom will decay, but given a large number of similar atoms, the decay rate, on average, is predictable. Randomness is a lack of order Purpose, cause, or predictability

The SI unit of radioactive decay (the phenomenon of natural and artificial radioactivity) is the becquerel (Bq). The becquerel (symbol Bq) is the SI derived unit of radioactivity. One Bq is defined as one transformation (or decay) per second. Since any reasonably-sized sample of radioactive material contains many atoms, a Bq is a tiny measure of activity; amounts on the order of TBq (terabecquerel) or GBq (gigabecquerel) are commonly used. Another unit of (radio)activity is the curie, Ci, which was originally defined as the activity of one gram of pure radium, isotope Ra-226. A CURIE (short for Compact URI) is an abbreviated URI expressed in CURIE syntax and may be found in both XML and non-XML grammars Radium (ˈreɪdiəm is a radioactive Chemical element which has the symbol Ra and Atomic number 88 Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides At present it is equal (by definition) to the activity of any radionuclide decaying with a disintegration rate of 3. 7 × 10¹⁰ Bq. The use of Ci is presently discouraged by SI.

The trefoil symbol is used to indicate radioactive material. Hazard symbols are easily recognizable symbols designed to warn about hazardous materials or locations

Ionizing radiation hazard symbol (recently introduced). ^[1]

Explanation

The neutrons and protons that constitute nuclei, as well as other particles that may approach them, are governed by several interactions. 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 The strong nuclear force, not observed at the familiar macroscopic scale, is the most powerful force over subatomic distances. The nuclear force (or nucleon-nucleon interaction or residual strong force) is the force between two or more Nucleons It is responsible for Macroscopic is commonly used to describe physical objects that are measurable and observable by the Naked eye. The electrostatic force is also significant, while the weak nuclear force is responsible for beta decay. ---- Bold text Coulomb's law', developed in the 1780s by French physicist Charles Augustin de Coulomb, may be stated in scalar form The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted

The interplay of these forces is simple. Some configurations of the particles in a nucleus have the property that, should they shift ever so slightly, the particles could fall into a lower-energy arrangement (with the extra energy moving elsewhere). In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός One might draw an analogy with a snowfield on a mountain: while friction between the snow crystals can support the snow's weight, the system is inherently unstable with regard to a lower-potential-energy state, and a disturbance may facilitate the path to a greater entropy state (i. Friction is the Force resisting the relative motion of two Surfaces in contact or a surface in contact with a fluid (e In Thermodynamics (a branch of Physics) entropy, symbolized by S, is a measure of the unavailability of a system ’s Energy e. , towards the ground state where heat will be produced, and thus total energy is distributed over a larger number of quantum states). In Quantum physics, a quantum state is a mathematical object that fully describes a quantum system. Thus, an avalanche results. This article refers to the natural event For other uses see Avalanche (disambiguation An avalanche is an abrupt and rapid flow of snow often The total energy does not change in this process, but because of entropy effects, avalanches only happen in one direction, and the end of this direction, which is dictated by the largest number of chance-mediated ways to distribute available energy, is what we commonly refer to as the "ground state". In Quantum mechanics, a stationary state is an Eigenstate of a Hamiltonian, or in other words a state of definite energy

Such a collapse (a decay event) requires a specific activation energy. In Chemistry, activation energy, also called midnight energy, is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined In the case of a snow avalanche, this energy classically comes as a disturbance from outside the system, although such disturbances can be arbitrarily small. In the case of an excited atomic nucleus, the arbitrarily small disturbance comes from quantum vacuum fluctuations. 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 virtual particle is a particle that exists for a limited time and space introducing uncertainty in their energy and momentum due to the Heisenberg Uncertainty A nucleus (or any excited system in quantum mechanics) is unstable, and can thus spontaneously stabilize to a less-excited system. This process is driven by entropy considerations: the energy does not change, but at the end of the process, the total energy is more diffused in spacial volume. The resulting transformation alters the structure of the nucleus. Such a reaction is thus a nuclear reaction, in contrast to chemical reactions, which also are driven by entropy, but which involve changes in the arrangement of the outer electrons of atoms, rather than their nuclei. In Nuclear physics, a nuclear reaction is the process in which two nuclei or nuclear particles collide to produce products different from the initial particles 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 The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J

Some nuclear reactions do involve external sources of energy, in the form of collisions with outside particles. In Nuclear physics, a nuclear reaction is the process in which two nuclei or nuclear particles collide to produce products different from the initial particles However, these are not considered decay. Rather, they are examples of induced nuclear reactions. In Nuclear physics, a nuclear reaction is the process in which two nuclei or nuclear particles collide to produce products different from the initial particles Nuclear fission and fusion are common types of induced nuclear reactions. 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 In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus

Discovery

Radioactivity was first discovered in 1896 by the French scientist Henri Becquerel, while working on phosphorescent materials. This article is about the country For a topic outline on this subject see List of basic France topics. Antoine Henri Becquerel (15 December 1852 &ndash 25 August 1908 was a French Physicist, Nobel laureate, and one of the discoverers of Radioactivity Phosphorescence is a specific type of Photoluminescence related to fluorescence. These materials glow in the dark after exposure to light, and he thought that the glow produced in cathode ray tubes by X-rays might be connected with phosphorescence. The cathode ray tube (CRT is a Vacuum tube containing an Electron gun (a source of electrons and a Fluorescent screen with internal or X-radiation (composed of X-rays) is a form of Electromagnetic radiation. He wrapped a photographic plate in black paper and placed various phosphorescent minerals on it. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific All results were negative until he used uranium salts. Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the The result with these compounds was a deep blackening of the plate.

It soon became clear that the blackening of the plate had nothing to do with phosphorescence, because the plate blackened when the mineral was in the dark. Non-phosphorescent salts of uranium and metallic uranium also blackened the plate. Clearly there was a form of radiation that could pass through paper that was causing the plate to blacken.

Alpha particles may be completely stopped by a sheet of paper, beta particles by aluminum shielding. Gamma rays can only be reduced by much more substantial barriers, such as a very thick layer of lead.

At first it seemed that the new radiation was similar to the then recently discovered X-rays. Further research by Becquerel, Marie Curie, Pierre Curie, Ernest Rutherford and others discovered that radioactivity was significantly more complicated. Pierre Curie (15 May 1859 &ndash 19 April 1906 was a French physicist, a pioneer in Crystallography, Magnetism, Piezoelectricity Ernest Rutherford 1st Baron Rutherford of Nelson, OM, PC, FRS (30 August 1871 – 19 October 1937 was a New Zealand Physicist Different types of decay can occur, but Rutherford was the first to realize that they all occur with the same mathematical approximately exponential formula (see below).

As for types of radioactive radiation, it was found that an electric or magnetic field could split such emissions into three types of beams. 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 In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges For lack of better terms, the rays were given the alphabetic names alpha, beta and gamma, still in use today. The Greek alphabet (Ελληνικό αλφάβητο is a set of twenty-four letters that has been used to write the Greek language since the late 9th or early Alpha particles (named after and denoted by the first letter in the Greek alphabet, α consist of two Protons and two Neutrons bound together into a Beta particles are high-energy high-speed Electrons or Positrons emitted by certain types of Radioactive nuclei such as Potassium -40 Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions It was obvious from the direction of electromagnetic forces that alpha rays carried a positive charge, beta rays carried a negative charge, and gamma rays were neutral. Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of 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 In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions From the magnitude of deflection, it was clear that alpha particles were much more massive than beta particles. Alpha particles (named after and denoted by the first letter in the Greek alphabet, α consist of two Protons and two Neutrons bound together into a Beta particles are high-energy high-speed Electrons or Positrons emitted by certain types of Radioactive nuclei such as Potassium -40 Passing alpha particles through a very thin glass window and trapping them in a discharge tube allowed researchers to study the emission spectrum of the resulting gas, and ultimately prove that alpha particles are helium nuclei. A neon lamp is a Gas discharge Lamp containing primarily Neon gas at low Pressure. An element's 'emission spectrum' is the relative intensity of Electromagnetic radiation of each Frequency it emits when it is Heated (or more generally when Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Other experiments showed the similarity between beta radiation and cathode rays; they are both streams of electrons, and between gamma radiation and X-rays, which are both high energy electromagnetic radiation. Cathode rays (also called an electron beam or e-beam) are streams of Electrons observed in Vacuum tubes i The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter.

Although alpha, beta, and gamma are most common, other types of decay were eventually discovered. Shortly after discovery of the neutron in 1932, it was discovered by Enrico Fermi that certain rare decay reactions yield neutrons as a decay particle. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. Isolated proton emission was eventually observed in some elements. Proton emission (also known as proton radioactivity is a type of radioactive decay in which a Proton is ejected from a nucleus. Shortly after the discovery of the positron in cosmic ray products, it was realized that the same process that operates in classical beta decay can also produce positrons (positron emission), analogously to negative electrons. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted Positron emission is a type of Beta decay, sometimes referred to as " beta plus " (&beta+ Each of the two types of beta decay acts to move a nucleus toward a ratio of neutrons and protons which has the least energy for the combination. Finally, in a phenomenon called cluster decay, specific combinations of neutrons and protons other than alpha particles were spontaneously emitted from atoms on occasion. Cluster decay is a type of nuclear decay in which a Radioactive Atom emits a cluster of Neutrons and Protons heavier than an Alpha particle

Still other types of radioactive decay were found which emit previously seen particles, but by different mechanisms. An example is internal conversion, which results in electron and sometimes high energy photon emission, even though it involves neither beta nor gamma decay. Internal conversion is a Radioactive decay process where an excited nucleus interacts with an Electron in one of the lower electron shells causing the

The early researchers also discovered that many other chemical elements besides uranium have radioactive isotopes. 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. 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 A systematic search for the total radioactivity in uranium ores also guided Marie Curie to isolate a new element polonium and to separate a new element radium from barium. Polonium (pəˈloʊniəm is a Chemical element with the symbol Po and Atomic number 84 discovered in 1898 by Marie and Pierre Curie Radium (ˈreɪdiəm is a radioactive Chemical element which has the symbol Ra and Atomic number 88 Barium (ˈbɛəriəm is a Chemical element. It has the symbol Ba, and Atomic number 56 The two elements' chemical similarity would otherwise have made them difficult to distinguish.

The danger classification sign of radioactive materials

The dangers of radioactivity and of radiation were not immediately recognized. Acute effects of radiation were first observed in the use of X-rays when the Serbo-Croatian-American electric engineer Nikola Tesla intentionally subjected his fingers to X-rays in 1896. There have already been discussions about Tesla's ethnicity on the talk page He published his observations concerning the burns that developed, though he attributed them to ozone rather than to X-rays. His injuries healed later.

The genetic effects of radiation, including the effects on cancer risk, were recognized much later. In 1927 Hermann Joseph Muller published research showing genetic effects, and in 1946 was awarded the Nobel prize for his findings. Hermann Joseph “HJ” Muller ( December 21 1890 &ndash April 5 1967) was an American Geneticist, educator and The Nobel Prize (Nobelpriset (Nobelprisen is a Swedish prize established in the 1895 will of Swedish chemist Alfred Nobel; it was first awarded in Peace, Literature

Before the biological effects of radiation were known, many physicians and corporations had begun marketing radioactive substances as patent medicine and radioactive quackery. Patent medicine is the somewhat misleading term given to various medical Compounds sold under a variety of names and labels though they were for the most part actually Radioactive quackery refers to various products sold during the early 20th century after the discovery of Radioactivity, which promised radioactivity as a cure for various ills Examples were radium enema treatments, and radium-containing waters to be drunk as tonics. An enema (plural enemata or enemas) is the procedure of introducing liquids into the Rectum and colon via the Anus. Marie Curie spoke out against this sort of treatment, warning that the effects of radiation on the human body were not well understood (Curie later died from aplastic anemia assumed due to her work with radium, but later examination of her bones showed that she had been a careful laboratory worker and had a low burden of radium. A more likely cause was her exposure to unshielded X-ray tubes while a volunteer medical worker in WWI). By the 1930s, after a number of cases of bone necrosis and death in enthusiasts, radium-containing medical products had nearly vanished from the market.

Modes of decay

Radionuclides can undergo a number of different reactions. These are summarized in the following table. A nucleus with mass number A and atomic number Z is represented as (A, Z). The mass number ( A) also called atomic mass number or nucleon number, is the total number of Protons and Neutrons (together known as See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton The column "Daughter nucleus" indicates the difference between the new nucleus and the original nucleus. Thus, (A–1, Z) means that the mass number is one less than before, but the atomic number is the same as before.

Radioactive decay results in a reduction of summed rest mass, which is converted to energy (the disintegration energy) according to the formula E = mc². 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 Alpha particles (named after and denoted by the first letter in the Greek alphabet, α consist of two Protons and two Neutrons bound together into a Proton emission (also known as proton radioactivity is a type of radioactive decay in which a Proton is ejected from a nucleus. Neutron emission is a type of Radioactive decay of atoms containing excess Neutrons in which a neutron is simply ejected from the nucleus Proton emission (also known as proton radioactivity is a type of radioactive decay in which a Proton is ejected from a nucleus. Spontaneous fission (SF is a form of Radioactive decay characteristic of very heavy Isotopes and is theoretically possible for any atomic nucleus whose mass is greater Cluster decay is a type of nuclear decay in which a Radioactive Atom emits a cluster of Neutrons and Protons heavier than an Alpha particle In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted In Physics, antineutrinos, the Antiparticles of Neutrinos are neutral particles produced in nuclear Beta decay. Positron emission is a type of Beta decay, sometimes referred to as " beta plus " (&beta+ In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted 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 Electron capture (sometimes called inverse beta decay) is a Decay mode for Isotopes that will occur when there are too many Protons in the In the process of Beta decay, unstable nuclei decay by converting a Neutron in the nucleus to a Proton and emitting an Electron and an electron Double electron capture is a Decay mode of Atomic nucleus. For a nuclide ( A, Z) with number of Nucleons A and Atomic Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions Internal conversion is a Radioactive decay process where an excited nucleus interacts with an Electron in one of the lower electron shells causing the Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object The term Mass in Special relativity usually refers to the Rest mass of the object which is the Newtonian mass as measured by an observer moving along with This energy is released as kinetic energy of the emitted particles. The energy remains associated with a measure of mass of the decay system invariant mass, inasmuch the kinetic energy of emitted particles contributes also to the total invariant mass of systems. Thus, the sum of rest masses of particles is not conserved in decay, but the system mass or system invariant mass (as also system total energy) is conserved.

Decay chains and multiple modes

The daughter nuclide of a decay event may also be unstable (radioactive). In this case, it will also decay, producing radiation. The resulting second daughter nuclide may also be radioactive. This can lead to a sequence of several decay events. Eventually a stable nuclide is produced. This is called a decay chain. In Nuclear science, the decay chain refers to the Radioactive decay of different discrete radioactive decay products as a chained series of transformations

An example is the natural decay chain of uranium-238 which is as follows:

• decays, through alpha-emission, with a half-life of 4. In Nuclear science, the decay chain refers to the Radioactive decay of different discrete radioactive decay products as a chained series of transformations Uranium-238 (U-238 is the most common isotope of Uranium found in nature Half-Life (computer-game page here It's already listed in the disambiguation page 5 billion years to thorium-234
• which decays, through beta-emission, with a half-life of 24 days to protactinium-234
• which decays, through beta-emission, with a half-life of 1. Thorium-234 is an Isotope of Thorium with 90 Protons and Electrons and 144 Neutrons. Protactinium ( Pa)Standard atomic mass 23103588(2 u The element has no stable isotopes 2 minutes to uranium-234
• which decays, through alpha-emission, with a half-life of 240 thousand years to thorium-230
• which decays, through alpha-emission, with a half-life of 77 thousand years to radium-226
• which decays, through alpha-emission, with a half-life of 1. Uranium-234 is an isotope of Uranium. In Natural uranium and uranium ore 234U occurs as an indirect Decay product of 238U Thorium-230 (230Th is a Radioactive Isotope of Thorium which can be used to date Corals and determine Ocean current Radium ( Ra) has no stable Isotopes A standard Atomic mass cannot be given 6 thousand years to radon-222
• which decays, through alpha-emission, with a half-life of 3. There are thirty four known Isotopes of Radon ( Rn) The most stable isotope is 222Rn which is a Decay product (daughter product of 8 days to polonium-218
• which decays, through alpha-emission, with a half-life of 3. Polonium (pəˈloʊniəm is a Chemical element with the symbol Po and Atomic number 84 discovered in 1898 by Marie and Pierre Curie 1 minutes to lead-214
• which decays, through beta-emission, with a half-life of 27 minutes to bismuth-214
• which decays, through beta-emission, with a half-life of 20 minutes to polonium-214
• which decays, through alpha-emission, with a half-life of 160 microseconds to lead-210
• which decays, through beta-emission, with a half-life of 22 years to bismuth-210
• which decays, through beta-emission, with a half-life of 5 days to polonium-210
• which decays, through alpha-emission, with a half-life of 140 days to lead-206, which is a stable nuclide. Lead ( Pb) has four stable Isotopes - 204Pb 206Pb 207Pb 208Pb and one common Radiogenic isotope Standard atomic mass 20898040(1 u Isotopes of Bismuth (Bi occurring within the radioactive Disintegration chains of Actinium Polonium ( Po) has 33 known isotopes, all of which are radioactive. Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly Standard atomic mass 20898040(1 u Isotopes of Bismuth (Bi occurring within the radioactive Disintegration chains of Actinium Polonium ( Po) has 33 known isotopes, all of which are radioactive. Lead ( Pb) has four stable Isotopes - 204Pb 206Pb 207Pb 208Pb and one common Radiogenic isotope

Some radionuclides may have several different paths of decay. For example, approximately 36% of bismuth-212, decays, through alpha-emission, to thallium-208 while approximately 64% of bismuth-212 decays, through beta-emission, to polonium-212. Standard atomic mass 20898040(1 u Isotopes of Bismuth (Bi occurring within the radioactive Disintegration chains of Actinium Thallium ( Tl) has 25 Isotopes which have Atomic masses that range from 184 to 210 Standard atomic mass 20898040(1 u Isotopes of Bismuth (Bi occurring within the radioactive Disintegration chains of Actinium Polonium ( Po) has 33 known isotopes, all of which are radioactive. Both the thallium-208 and the polonium-212 are radioactive daughter products of bismuth-212, and both decay directly to stable lead-208. Thallium ( Tl) has 25 Isotopes which have Atomic masses that range from 184 to 210 Polonium ( Po) has 33 known isotopes, all of which are radioactive. Standard atomic mass 20898040(1 u Isotopes of Bismuth (Bi occurring within the radioactive Disintegration chains of Actinium Lead ( Pb) has four stable Isotopes - 204Pb 206Pb 207Pb 208Pb and one common Radiogenic isotope

Occurrence and applications

According to the Big Bang theory, stable isotopes of the lightest five elements (H, He, and traces of Li, Be, and B) were produced very shortly after the emergence of the universe, in a process called Big Bang nucleosynthesis. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 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 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. In Physical cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than those of H-1 (i These lightest stable nuclides (including deuterium) survive to today, but any radioactive isotopes of the light elements produced in the Big Bang (such as tritium) have long since decayed. 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. Isotopes of elements heavier than boron were not produced at all in the Big Bang, and these first five elements do not have any long-lived radioisotopes. Thus, all radioactive nuclei are therefore relatively young with respect to the birth of the universe, having formed later in various other types of nucleosynthesis in stars (particularly supernovae), and also during ongoing interactions between stable isotopes and energetic particles. Nucleosynthesis is the process of creating new atomic nuclei from preexisting Nucleons (protons and neutrons 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 A supernova (plural supernovae or supernovas) is a stellar Explosion. For example, carbon-14, a radioactive nuclide with a half-life of only 5730 years, is constantly produced in Earth's upper atmosphere due to interactions between cosmic rays and nitrogen. Carbon-14, 14C, or radiocarbon, is a Radioactive isotope of Carbon discovered on February 27, 1940, by

Radioactive decay has been put to use in the technique of radioisotopic labeling, used to track the passage of a chemical substance through a complex system (such as a living organism). Isotopic labeling is a technique for tracking the passage of a sample of substance through a system A sample of the substance is synthesized with a high concentration of unstable atoms. The presence of the substance in one or another part of the system is determined by detecting the locations of decay events.

On the premise that radioactive decay is truly random (rather than merely chaotic), it has been used in hardware random-number generators. Randomness is a lack of order Purpose, cause, or predictability In Mathematics, chaos theory describes the behavior of certain dynamical systems – that is systems whose state evolves with time – that may exhibit dynamics that In Computing, a hardware random number generator is an apparatus that generates Random numbers from a physical process Because the process is not thought to vary significantly in mechanism over time, it is also a valuable tool in estimating the absolute ages of certain materials. For geological materials, the radioisotopes and some of their decay products become trapped when a rock solidifies, and can then later be used (subject to many well-known qualifications) to estimate the date of the solidification. These include checking the results of several simultaneous processes and their products against each other, within the same sample. In a similar fashion, and also subject to qualification, the rate of formation of carbon-14 in various eras, the date of formation of organic matter within a certain period related to the isotope's half-live may be estimated, because the carbon-14 becomes trapped when the organic matter grows and incorporates the new carbon-14 from the air. Thereafter, the amount of carbon-14 in organic matter decreases according to decay processes which may also be independently cross-checked by other means (such as checking the carbon-14 in individual tree rings, for example).

Radioactive decay rates

The decay rate, or activity, of a radioactive substance are characterized by:

Constant quantities:

• half life — symbol t_{1 / 2} — the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value. Half-Life (computer-game page here It's already listed in the disambiguation page
• mean lifetime — symbol τ — the average lifetime of a radioactive particle. Given an assembly of elements the number of which decreases ultimately to zero the lifetime (also called the mean lifetime) is a certain number that characterizes the rate
• decay constant — symbol λ — the inverse of the mean lifetime. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value

(Note that although these are constants, they are associated with statistically random behavior of substances, and predictions using these constants are less accurate for small number of atoms. )

Time-variable quantities:

• Total activity — symbol A — number of decays an object undergoes per second.
• Number of particles — symbol N — the total number of particles in the sample.
• Specific activity — symbol S_A — number of decays per second per amount of substance. (The "amount of substance" can be the unit of either mass or volume. )

These are related as follows:

where

is the initial amount of active substance — substance that has the same percentage of unstable particles as when the substance was formed.

Activity measurements

The units in which activities are measured are: becquerel (symbol Bq) = number of disintegrations per second; curie (Ci) = 3. The becquerel (symbol Bq) is the SI derived unit of radioactivity. A CURIE (short for Compact URI) is an abbreviated URI expressed in CURIE syntax and may be found in both XML and non-XML grammars 7 × 10¹⁰ disintegrations per second. Low activities are also measured in disintegrations per minute (dpm).

Decay timing

See also: exponential decay

As discussed above, the decay of an unstable nucleus is entirely random and it is impossible to predict when a particular atom will decay. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value However, it is equally likely to decay at any time. Therefore, given a sample of a particular radioisotope, the number of decay events –dN expected to occur in a small interval of time dt is proportional to the number of atoms present. If N is the number of atoms, then the probability of decay (– dN/N) is proportional to dt:

Particular radionuclides decay at different rates, each having its own decay constant (λ). Lambda (uppercase Λ, lowercase λ; Λάμβδα or el Λάμδα Lamda is the 11th letter of the Greek alphabet. The negative sign indicates that N decreases with each decay event. The solution to this first-order differential equation is the following function:

Where N₀ is the amount of N at time zero (t = 0). A differential equation is a mathematical Equation for an unknown function of one or several variables that relates the values of the The Mathematical concept of a function expresses dependence between two quantities one of which is given (the independent variable, argument of the function The second equation recognizes that the differential decay constant λ has units of 1/time, and can thus also be represented as 1/τ, where τ is a characteristic time for the process. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value This characteristic time is called the time constant of the process. In Physics and Engineering, the time constant usually denoted by the Greek letter \tau, (tau characterizes the Frequency In radioactive decay, this process time constant it also the mean lifetime for decaying atoms. Given an assembly of elements the number of which decreases ultimately to zero the lifetime (also called the mean lifetime) is a certain number that characterizes the rate Each atom "lives" for a finite amount of time before it decays, and it may be shown that this mean lifetime is the arithmetic mean of all the atoms' lifetimes, and that it is τ, which again is related to the decay constant as follows:

The previous exponential function generally represents the result of exponential decay. In Mathematics and Statistics, the arithmetic Mean (or simply the mean) of a list of numbers is the sum of all the members of the list divided A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value It is only an approximate solution, for two reasons. Firstly, the exponential function is continuous, but the physical quantity N can only take non-negative integer values. The exponential function is a function in Mathematics. The application of this function to a value x is written as exp( x) In Mathematics, a continuous function is a function for which intuitively small changes in the input result in small changes in the output In Mathematics, a natural number (also called counting number) can mean either an element of the set (the positive Integers or an Secondly, because it describes a random process, it is only statistically true. However, in most common cases, N is a very large number and the function is a good approximation.

A more commonly used parameter is the half-life. Half-Life (computer-game page here It's already listed in the disambiguation page Given a sample of a particular radionuclide, the half-life is the time taken for half the radionuclide's atoms to decay. The half life is related to the decay constant as follows:

This relationship between the half-life and the decay constant shows that highly radioactive substances are quickly spent, while those that radiate weakly endure longer. Half-lives of known radionuclides vary widely, from more than 10¹⁹ years (such as for very nearly stable nuclides, e. To help compare Orders of magnitude of different times this page lists times longer than 1019 Seconds (317 billion years g. ²⁰⁹Bi), to 10^-23 seconds for highly unstable ones.

References

1. ^ This symbol is included in ISO 21482:2007. ISO International Standards are protected by copyright and may be purchased from ISO or its members (please visit www. iso. org for more information). ISO has not reviewed the accuracy or veracity of this information.

• "Radioactivity", Encyclopædia Britannica. 2006. Encyclopædia Britannica Online. 18 Dec. 2006

See also

External links

• General information
• Nomenclature of nuclear chemistry
• Some theoretical questions of nuclear stability
• Decay heat rate|quantity calculation
• Specific activity and related topics. Nuclear Pharmacy involves the preparation of Radioactive materials that will be used to diagnose and treat specific diseases Nuclear medicine is a branch of Medicine and Medical imaging that uses the nuclear properties of matter in diagnosis and therapy Nuclear physics is the field of Physics that studies the building blocks and interactions of Atomic nuclei. Radioactivity can be used in life sciences as a Radiolabel to easily visualise components or target molecules in a biological system A Poisson process, named after the French mathematician Siméon-Denis Poisson (1781 &ndash 1840 is the Stochastic process in which events occur continuously and Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy Radiation therapy (or radiotherapy) is the medical use of Ionizing radiation as part of Cancer treatment to control Malignant Radioactive contamination is the uncontrolled distribution of radioactive material in a given environment Radiometric dating (often called radioactive dating) is a technique used to date materials usually based on a comparison between the observed abundance of a naturally occurring Actinides in the environment refer to the sources environmental behaviour and effects of Actinides in the environment. Half-Life (computer-game page here It's already listed in the disambiguation page A fallout shelter is an enclosed space specially designed to protect occupants from radioactive debris or fallout resulting from a Nuclear explosion. Particle decay is the spontaneous process of one Elementary particle transforming into other elementary particles
• The Lund/LBNL Nuclear Data Search - Contains tabulated information on radioactive decay types and energies.

References