1 (none) ← hydrogen → helium - ↑ H ↓ Li Periodic table - Extended periodic table
General
Name, symbol, number	hydrogen, H, 1
Chemical series	nonmetals
Group, period, block	1, 1, s
Appearance	colorless
Standard atomic weight	1.00794(7) g·mol−1
Electron configuration	1s1
Electrons per shell	1
Physical properties
Phase	gas
Density	(0 °C, 101. 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 This is a typical display of the periodic table of the elements and contains the symbol and Atomic number of each element Wikipedia talkFeatured lists for an explanation of this and other inclusion tags below -->This is a list of Chemical elements, sorted by name Wikipedia talkFeatured lists for an explanation of this and other inclusion tags below -->This is a list of chemical elements by symbol, including the A table of Chemical elements ordered by Atomic number and color coded according to type of element In Chemistry a group, also known as a family, is a vertical column in the Periodic table of the Chemical elements There are 18 groups in Nonmetal is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties every element in the In Chemistry a group, also known as a family, is a vertical column in the Periodic table of the Chemical elements There are 18 groups in In the Periodic table of the elements, a period is a horizontal row of the table A block of the Periodic table of elements is a set of adjacent groups The respective highest-energy electrons in each element in a block belong to the same Atomic Trends The alkali metals show a number of trends when moving down the group - for instance decreasing electronegativity increasing reactivity and decreasing melting and boiling A period 1 element is one of the Chemical elements in the first row (or period) of the periodic table of the chemical elements. See also Electron configuration 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 To help compare different orders of magnitude, the following list describes various Mass levels between 10&minus36&thinsp kg and 1053&thinspkg Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) In Atomic physics and Quantum chemistry, electron configuration is the arrangement of Electrons in an Atom, Molecule, or other The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. 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 This page is about the physical properties of gas as a state of matter The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 325 kPa) 0. 08988 g/L
Melting point	14. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. 01 K (−259. 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 14 °C, −434. The Celsius Temperature scale was previously known as the centigrade scale. 45 °F)
Boiling point	20. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid 28 K (−252. 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 87 °C, −423. The Celsius Temperature scale was previously known as the centigrade scale. 17 °F)
Triple point	13. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 In Thermodynamics, the triple point of a substance is the Temperature and Pressure at which three phases (for example Gas, Liquid 8033 K (-259°C), 7. The Celsius Temperature scale was previously known as the centigrade scale. 042 kPa
Critical point	32. In Physical chemistry, Thermodynamics, Chemistry and Condensed matter physics, a critical point, also called a critical state 97 K, 1. 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 293 MPa
Heat of fusion	(H2) 0. The standard Enthalpy of fusion (symbol \Delta{}H_{fus} also known as the heat of fusion or specific melting heat, is the amount of 117 kJ·mol−1
Heat of vaporization	(H2) 0. The joule per mole (symbol J·mol-1 is an SI derived unit of energy per amount of material The enthalpy of vaporization, (symbol \Delta{}_{v}H also known as the heat of vaporization or heat of evaporation, is the Energy required 904 kJ·mol−1
Specific heat capacity	(25 °C) (H2) 28. The joule per mole (symbol J·mol-1 is an SI derived unit of energy per amount of material Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the Temperature of a unit quantity 836 J·mol−1·K−1
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K         15 20
Atomic properties
Crystal structure	hexagonal
Oxidation states	1, −1 (amphoteric oxide)
Electronegativity	2. Vapor pressure (also known as equilibrium vapor pressure or saturation vapor pressure) is the Pressure of a Vapor in equilibrium In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. The oxidation number of a central atom in a coordination compound is the charge that it would have if all the Ligands were removed along with the Electron pairs " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons 20 (Pauling scale)
Ionization energies	1st: 1312. The ionization potential, ionization energy or EI of an Atom or Molecule is the Energy required to remove an Electron 0 kJ·mol−1
Atomic radius	25 pm
Atomic radius (calc. The joule per mole (symbol J·mol-1 is an SI derived unit of energy per amount of material 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 picometre ( American spelling: picometer, symbol pm) is a unit of Length in the Metric system, equal to one trillionth )	53 pm
Covalent radius	37 pm
Van der Waals radius	120 pm
Miscellaneous
Thermal conductivity	(300 K) 180. The covalent radius, r cov is a measure of the size of Atom which forms part of a Covalent bond. Van der Waals Volume The van der Waals volume, V, also called the atomic volume or molecular volume, is the atomic property most directly In Physics, thermal conductivity, k is the property of a material that indicates its ability to conduct Heat. 5 m W·m−1·K−1
Speed of sound	(gas, 27 °C) 1310 m/s
CAS registry number	1333-74-0
Selected isotopes
Main article: Isotopes of hydrogen iso NA half-life DM DE (MeV) DP 1H 99. Sound is a vibration that travels through an elastic medium as a Wave. CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to Hydrogen ( H) (Standard atomic mass 100794(7 u) has three naturally occurring isotopes, denoted 1H 2H Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides In Chemistry, natural abundance (NA refers to the abundance Isotopes of a Chemical element as naturally found on a planet Half-Life (computer-game page here It's already listed in the disambiguation page Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. The decay energy is the Energy released by a Nuclear decay. The energy difference of the Reactants is often written as Q: where Q In Nuclear physics, a decay product, also known as a daughter product, daughter isotope or daughter nuclide, is a Nuclide 985% 1H is stable with 0 neutrons 2H 0. Stable isotopes are chemical isotopes that are not Radioactive (to current knowledge This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth 015% 2H is stable with 1 neutrons 3H trace 12. Stable isotopes are chemical isotopes that are not Radioactive (to current knowledge This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. A trace radioisotope is a Radioisotope that occurs naturally in trace amounts (i 32 y β− 0. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted 019 3He
References
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Hydrogen (pronounced /ˈhaɪdrədʒən/^[1]) is the chemical element with atomic number 1. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Recommended values for many properties of the elements together with various references are collected on these data pages 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 It is represented by the symbol H. See also Chemical formula. A chemical symbol is an Abbreviation or shortened version of the name of a Chemical element At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H₂. In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made Nonmetal is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties every element in the Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of Diatomic molecules are molecules made only of two Atoms of either the same or different Chemical elements The prefix di- means two in Greek This page is about the physical properties of gas as a state of matter A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes With an atomic mass of 1. 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 00794 amu, hydrogen is the lightest element.

Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass. See also Abundances of the elements (data page The abundance of a Chemical element measures how relatively common the element is or how much of the element ^[2] Stars in the main sequence are mainly composed of hydrogen in its plasma 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 The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound Elemental hydrogen is relatively rare on Earth, and is industrially produced from hydrocarbons such as methane, after which most elemental hydrogen is used "captively" (meaning locally at the production site), with the largest markets about equally divided between fossil fuel upgrading (e. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Fossil fuels or mineral fuels are fossil source Fuels that is Hydrocarbons found within the top layer of the Earth’s crust. g. , hydrocracking) and ammonia production (mostly for the fertilizer market). In Petroleum geology and Chemistry, cracking is the process whereby complex organic Molecules such as Kerogens or heavy Hydrocarbons Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Hydrogen may be produced from water using the process of electrolysis, but this process is presently significantly more expensive commercially than hydrogen production from natural gas. In chemistry and manufacturing electrolysis is a method of separating chemically bonded elements and compounds by passing an Electric current ^[3]

The most common naturally occurring isotope of hydrogen, known as protium, has a single proton and no neutrons. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides A hydrogen atom is an atom of the chemical element Hydrogen. The electrically neutral The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. In ionic compounds it can take on either a positive charge (becoming a cation composed of a bare proton) or a negative charge (becoming an anion known as a hydride). In Chemistry, an ionic compound is a Chemical compound in which Ions are held together in a lattice structure by Ionic bonds Usually the positively 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 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 Hydride is the name given to the negative Ion of Hydrogen, H− Hydrogen can form compounds with most elements and is present in water and most organic compounds. Water is a common Chemical substance that is essential for the survival of all known forms of Life. An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. It plays a particularly important role in acid-base chemistry, in which many reactions involve the exchange of protons between soluble molecules. As the only neutral atom for which the Schrödinger equation can be solved analytically, study of the energetics and bonding of the hydrogen atom has played a key role in the development of quantum mechanics. In Physics, especially Quantum mechanics, the Schrödinger equation is an equation that describes how the Quantum state of a Physical system Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons

The solubility and characteristics of hydrogen with various metals are very important in metallurgy (as many metals can suffer hydrogen embrittlement^[4]) and in developing safe ways to store it for use as a fuel. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Metallurgy is a domain of Materials science that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their Hydrogen embrittlement (or hydrogen grooving) is the process by which various metals most importantly high-strength Steel, become brittle and crack following exposure ^[5] Hydrogen is highly soluble in many compounds composed of rare earth metals and transition metals^[6] and can be dissolved in both crystalline and amorphous metals. Rare earth elements and rare earth metals are according to IUPAC, the collection of seventeen Chemical elements in the Periodic table, namely In Chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings It commonly refers to any element in In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating An amorphous solid is a Solid in which there is no Long-range order of the positions of the Atoms (Solids in which there is long-range atomic order are ^[7] Hydrogen solubility in metals is influenced by local distortions or impurities in the metal crystal lattice. In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. ^[8]

Combustion

Hydrogen is highly combustible in air. It burned rapidly in the Hindenburg disaster on May 6, 1937. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Events 1527 - Spanish and German troops sack Rome; some consider this the end of the Renaissance. Year 1937 ( MCMXXXVII) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar.

Hydrogen gas is highly flammable and will burn at concentrations of 4% or more H₂ in air. ^[9] The enthalpy of combustion for hydrogen is −286 kJ/mol;^[10] it burns according to the following balanced equation. In Thermodynamics and molecular chemistry, the enthalpy (denoted as H, h, or rarely as χ) is a quotient or description of

2 H₂(g) + O₂(g) → 2 H₂O(l) + 572  kJ (286 kJ/mol)^[11]

When mixed with oxygen across a wide range of proportions, hydrogen explodes upon ignition. Hydrogen burns violently in air. It ignites automatically at a temperature of 560 °C. ^[12] Pure hydrogen-oxygen flames burn in the ultraviolet color range and are nearly invisible to the naked eye, as illustrated by the faintness of flame from the main Space Shuttle engines (as opposed to the easily visible flames from the SRBs). Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays NASA 's Space Shuttle, officially called the Space Transportation System ( STS) is the Spacecraft currently used by the United States The Space Shuttle Solid Rocket Boosters (SRBs are the pair of large solid rockets used by the Space Shuttle during the first two minutes of powered flight Thus it is difficult to visually detect if a hydrogen leak is burning. The explosion of the Hindenburg airship was an infamous case of hydrogen combustion (pictured); the cause is debated, but combustible materials in the ship's skin were responsible for the coloring of the flames. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout ^[13] Another characteristic of hydrogen fires is that the flames tend to ascend rapidly with the gas in air, as illustrated by the Hindenburg flames, causing less damage than hydrocarbon fires. Two-thirds of the Hindenburg passengers survived the fire, and many of the deaths which occurred were from falling or from diesel fuel burns. ^[14]

H₂ reacts directly with other oxidizing elements. A violent and spontaneous reaction can occur at room temperature with chlorine and fluorine, forming the corresponding hydrogen halides: hydrogen chloride and hydrogen fluoride. Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Structure HF forms orthorhombic crystals consisting of zig-zag chains of HF molecules ^[15]

Electron energy levels

Main article: Hydrogen atom

Depiction of a hydrogen atom showing the diameter as about twice the Bohr model radius (image not to scale). A hydrogen atom is an atom of the chemical element Hydrogen. The electrically neutral In Atomic physics, the Bohr model created by Niels Bohr depicts the Atom as a small positively charged nucleus surrounded by Electrons

The ground state energy level of the electron in a hydrogen atom is −13. In Quantum mechanics, a stationary state is an Eigenstate of a Hamiltonian, or in other words a state of definite energy 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 6 eV, which is equivalent to an ultraviolet photon of roughly 92 nm. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International ^[16]

The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, which conceptualizes the electron as "orbiting" the proton in analogy to the Earth's orbit of the sun. In Atomic physics, the Bohr model created by Niels Bohr depicts the Atom as a small positively charged nucleus surrounded by Electrons However, the electromagnetic force attracts electrons and protons to one another, while planets and celestial objects are attracted to each other by gravity. Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of Gravitation is a natural Phenomenon by which objects with Mass attract one another Because of the discretization of angular momentum postulated in early quantum mechanics by Bohr, the electron in the Bohr model can only occupy certain allowed distances from the proton, and therefore only certain allowed energies. 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 Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons ^[17]

A more accurate description of the hydrogen atom comes from a purely quantum mechanical treatment that uses the Schrödinger equation or the equivalent Feynman path integral formulation to calculate the probability density of the electron around the proton. In Physics, especially Quantum mechanics, the Schrödinger equation is an equation that describes how the Quantum state of a Physical system This article is about a formulation of quantum mechanics For integrals along a path also known as line or contour integrals see Line integral. In Quantum mechanics, a probability amplitude is a complex -valued function that describes an uncertain or unknown quantity ^[18]

Elemental molecular forms

First tracks observed in liquid hydrogen bubble chamber at the Bevatron

There are two different types of diatomic hydrogen molecules that differ by the relative spin of their nuclei. A bubble chamber is a vessel filled with a superheated transparent Liquid (most often Liquid hydrogen) used to detect electrically charged The Bevatron was a Particle accelerator &mdash specifically a weak-focusing proton Synchrotron &mdash at Lawrence Berkeley National Laboratory which In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin ^[19] In the orthohydrogen form, the spins of the two protons are parallel and form a triplet state; in the parahydrogen form the spins are antiparallel and form a singlet. Each Hydrogen Molecule (H2 consists of two Hydrogen atoms linked by a Covalent bond. Each Hydrogen Molecule (H2 consists of two Hydrogen atoms linked by a Covalent bond. At standard temperature and pressure, hydrogen gas contains about 25% of the para form and 75% of the ortho form, also known as the "normal form". ^[20] The equilibrium ratio of orthohydrogen to parahydrogen depends on temperature, but since the ortho form is an excited state and has a higher energy than the para form, it is unstable and cannot be purified. Excitation is an elevation in energy level above an arbitrary baseline energy state At very low temperatures, the equilibrium state is composed almost exclusively of the para form. The physical properties of pure parahydrogen differ slightly from those of the normal form. ^[21] The ortho/para distinction also occurs in other hydrogen-containing molecules or functional groups, such as water and methylene. Methylene is the chemical species R2C named after Methane, in which two of the carbon atom's valence electrons form no bonds ^[22]

The uncatalyzed interconversion between para and ortho H₂ increases with increasing temperature; thus rapidly condensed H₂ contains large quantities of the high-energy ortho form that convert to the para form very slowly. ^[23] The ortho/para ratio in condensed H₂ is an important consideration in the preparation and storage of liquid hydrogen: the conversion from ortho to para is exothermic and produces enough heat to evaporate the hydrogen liquid, leading to loss of the liquefied material. In Thermodynamics, the word exothermic "outside heating" describes a process or reaction that releases Energy usually in the form of Heat, but Catalysts for the ortho-para interconversion, such as iron compounds, are used during hydrogen cooling. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 ^[24]

A molecular form called protonated molecular hydrogen, or H₃⁺, is found in the interstellar medium (ISM), where it is generated by ionization of molecular hydrogen from cosmic rays. Protonated molecular hydrogen, trihydrogen cation, or H3+ For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on It has also been observed in the upper atmosphere of the planet Jupiter. This molecule is relatively stable in the environment of outer space due to the low temperature and density. H₃⁺ is one of the most abundant ions in the Universe, and it plays a notable role in the chemistry of the interstellar medium. ^[25]

Compounds

Further information: Hydrogen compounds

Covalent and organic compounds

While H₂ is not very reactive under standard conditions, it does form compounds with most elements. Millions of hydrocarbons are known, but they are not formed by the direct reaction of elementary hydrogen and carbon (although synthesis gas production followed by the Fischer-Tropsch process to make hydrocarbons comes close to being an exception, as this begins with coal and the elemental hydrogen is generated in situ). In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Syngas (from syn thesis gas) is the name given to a gas mixture that contains varying amounts of Carbon monoxide and Hydrogen. The Fischer-Tropsch process (or Fischer-Tropsch Synthesis is a catalyzed chemical reaction in which synthesis gas ( Syngas) a mixture of Carbon monoxide Hydrogen can form compounds with elements that are more electronegative, such as halogens (e. " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions g. , F, Cl, Br, I); in these compounds hydrogen takes on a partial positive charge. ^[26] When bonded to fluorine, oxygen, or nitrogen, hydrogen can participate in a form of strong noncovalent bonding called hydrogen bonding, which is critical to the stability of many biological molecules. Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 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 A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen ^[27][28] Hydrogen also forms compounds with less electronegative elements, such as the metals and metalloids, in which it takes on a partial negative charge. The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across Metalloid is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties nearly every element These compounds are often known as hydrides. Hydride is the name given to the negative Ion of Hydrogen, H− ^[29]

Hydrogen forms a vast array of compounds with carbon. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Because of their general association with living things, these compounds came to be called organic compounds;^[30] the study of their properties is known as organic chemistry^[31] and their study in the context of living organisms is known as biochemistry. An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. Organic chemistry is a discipline within Chemistry which involves the scientific study of the structure properties composition reactions, and preparation Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as ^[32] By some definitions, "organic" compounds are only required to contain carbon. However, most of them also contain hydrogen, and since it is the carbon-hydrogen bond which gives this class of compounds most of its particular chemical characteristics, carbon-hydrogen bonds are required in some definitions of the word "organic" in chemistry. ^[30]

In inorganic chemistry, hydrides can also serve as bridging ligands that link two metal centers in a coordination complex. Inorganic chemistry is the branch of Chemistry concerned with the properties and behavior of Inorganic compounds This field covers all Chemical compounds A bridging Ligand is an Atom or a polyatomic entity that connects two or more Metal centres in a complex. The term complex in Chemistry is usually used to describe molecules or ensembles formed by the combination of Ligands and metal Ions. This function is particularly common in group 13 elements, especially in boranes (boron hydrides) and aluminium complexes, as well as in clustered carboranes. In chemistry a borane is a chemical compound of Boron and Hydrogen. Boron (ˈbɔərɒn is a Chemical element with Atomic number 5 and the chemical symbol B. WikipediaNaming A carborane is a cluster composed of Boron and Carbon atoms Like many of the related Boranes, these clusters are Polyhedra and are similarly ^[33]

Hydrides

Compounds of hydrogen are often called hydrides, a term that is used fairly loosely. Hydride is the name given to the negative Ion of Hydrogen, H− To chemists, the term "hydride" usually implies that the H atom has acquired a negative or anionic character, denoted H⁻. The existence of the hydride anion, suggested by Gilbert N. Lewis in 1916 for group I and II salt-like hydrides, was demonstrated by Moers in 1920 with the electrolysis of molten lithium hydride (LiH), that produced a stoichiometric quantity of hydrogen at the anode. Gilbert Newton Lewis ( October 23, 1875 - March 23, 1946) was a famous American physical chemist known for the discovery Lithium hydride ( Li[[Hydride H]] is the compound of Lithium and hydrogen Stoichiometry (sometimes called reaction stoichiometry to distinguish it from composition stoichiometry is the Calculation of Quantitative (measurable ^[34] For hydrides other than group I and II metals, the term is quite misleading, considering the low electronegativity of hydrogen. An exception in group II hydrides is BeH₂, which is polymeric. In lithium aluminium hydride, the AlH₄⁻ anion carries hydridic centers firmly attached to the Al(III). Lithium aluminium hydride ( Li[[Aluminium Al]] H4) commonly abbreviated to LAH, is a Reducing agent used in Organic synthesis Although hydrides can be formed with almost all main-group elements, the number and combination of possible compounds varies widely; for example, there are over 100 binary borane hydrides known, but only one binary aluminium hydride. ^[35] Binary indium hydride has not yet been identified, although larger complexes exist. Indium (ˈɪndiəm is a Chemical element with chemical symbol In and Atomic number 49 ^[36]

Protons and acids

See also: Acid-base reaction

Oxidation of hydrogen, in the sense of removing its electron, formally gives H⁺, containing no electrons and a nucleus which is usually composed of one proton. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive That is why H⁺ is often called a proton. This species is central to discussion of acids. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are Under the Bronsted-Lowry theory, acids are proton donors, while bases are proton acceptors.

A bare proton H⁺ cannot exist in solution because of its strong tendency to attach itself to atoms or molecules with electrons. However, the term 'proton' is used loosely to refer to positively charged or cationic hydrogen, denoted H⁺. 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

To avoid the convenient fiction of the naked "solvated proton" in solution, acidic aqueous solutions are sometimes considered to contain the hydronium ion (H₃O⁺), which is organized into clusters to form H₉O₄⁺. In Chemistry, hydronium is the obsolete name for the Cation H 3 O + derived from Protonation of Water ^[37] Other oxonium ions are found when water is in solution with other solvents. ^[38]

Although exotic on earth, one of the most common ions in the universe is the H₃⁺ ion, known as protonated molecular hydrogen or the triatomic hydrogen cation. Protonated molecular hydrogen, trihydrogen cation, or H3+ ^[39]

Isotopes

Main article: Isotopes of hydrogen

Protium, the most common isotope of hydrogen, has one proton and one electron. Hydrogen ( H) (Standard atomic mass 100794(7 u) has three naturally occurring isotopes, denoted 1H 2H Unique among all stable isotopes, it has no neutrons (see diproton for discussion of why others do not exist). A diproton is a hypothetical type of Helium nucleus consisting of two Protons and no Neutrons Diprotons are not stable this is due to spin-spin interactions

Hydrogen has three naturally occurring isotopes, denoted ¹H, ²H, and ³H. Other, highly unstable nuclei (⁴H to ⁷H) have been synthesized in the laboratory but not observed in nature. ^[40][41]

• ¹H is the most common hydrogen isotope with an abundance of more than 99. 98%. Because the nucleus of this isotope consists of only a single proton, it is given the descriptive but rarely used formal name protium. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive ^[42]
• ²H, the other stable hydrogen isotope, is known as deuterium and contains one proton and one neutron in its nucleus. Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. Deuterium is not radioactive, and does not represent a significant toxicity hazard. Water enriched in molecules that include deuterium instead of normal hydrogen is called heavy water. Heavy water is water which contains a higher proportion than normal of the Isotope Deuterium, as deuterium oxide, D2O or ²H2O Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for ¹H-NMR spectroscopy. Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is the name given to a technique which exploits the magnetic properties of certain nuclei ^[43] Heavy water is used as a neutron moderator and coolant for nuclear reactors. In Nuclear engineering, a neutron moderator is a medium which reduces the velocity of Fast neutrons thereby turning them into Thermal neutrons capable Deuterium is also a potential fuel for commercial nuclear fusion. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus ^[44]
• ³H is known as tritium and contains one proton and two neutrons in its nucleus. Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. It is radioactive, decaying into Helium-3 through beta decay with a half-life of 12. This article is about the elemental isotope For the record label Helium 3 see Muse or A&E Records. In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted Half-Life (computer-game page here It's already listed in the disambiguation page 32 years. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun ^[33] Small amounts of tritium occur naturally because of the interaction of cosmic rays with atmospheric gases; tritium has also been released during nuclear weapons tests. Nuclear weapons tests are experiments carried out to determine the effectiveness yield and explosive capability of Nuclear weapons Throughout the twentieth century most nations ^[45] It is used in nuclear fusion reactions,^[46] as a tracer in isotope geochemistry,^[47] and specialized in self-powered lighting devices. Isotope geochemistry is an aspect of Geology based upon study of the relative and absolute concentrations of the elements and their Isotopes in the Self-powered lighting is a generic term describing devices that emit light continuously without an external power source ^[48] Tritium has also been used in chemical and biological labeling experiments as a radiolabel. Isotopic labeling is a technique for tracking the passage of a sample of substance through a system ^[49]

Hydrogen is the only element that has different names for its isotopes in common use today. (During the early study of radioactivity, various heavy radioactive isotopes were given names, but such names are no longer used). The symbols D and T (instead of ²H and ³H) are sometimes used for deuterium and tritium, but the corresponding symbol P is already in use for phosphorus and thus is not available for protium. Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 ^[50] In its nomenclatural guidelines, the International Union of Pure and Applied Chemistry allows any of D, T, ²H, and ³H to be used, although ²H and ³H are preferred. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization ^[51]

Natural occurrence

NGC 604, a giant region of ionized hydrogen in the Triangulum Galaxy

Hydrogen is the most abundant element in the universe, making up 75% of normal matter by mass and over 90% by number of atoms. NGC 604 is an H II region inside the Triangulum Galaxy. It was discovered by William Herschel on September 11, 1784. An H II region (also known as Emission nebula) is a cloud of glowing Gas and plasma, sometimes several hundred Light-years across The Triangulum Galaxy (also known as Messier 33 or NGC 598) is a Spiral galaxy approximately 3 million light-years away in the In Chemistry, natural abundance (NA refers to the abundance Isotopes of a Chemical element as naturally found on a planet Baryons are the family of Subatomic particles with a Baryon number of 1 Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object ^[52] This element is found in great abundance in stars and gas giant planets. A gas giant (sometimes also known as a Jovian planet after the planet Jupiter, or giant planet) is a large Planet that is not primarily Molecular clouds of H₂ are associated with star formation. See also Solar nebula A molecular cloud, sometimes called a stellar nursery if Star formation is occurring within is a type of Interstellar Star Formation is the process by which dense parts of Molecular clouds collapse into a ball of plasma to form a Star. Hydrogen plays a vital role in powering stars through proton-proton reaction and CNO cycle nuclear fusion. 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 The proton-proton chain reaction is one of several fusion reactions by which Stars convert Hydrogen to Helium, the primary alternative being the The CNO cycle (for Carbon - Nitrogen - Oxygen) or sometimes Bethe-Weizsäcker-cycle, is one of two sets of fusion reactions In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus ^[53]

Throughout the universe, hydrogen is mostly found in the atomic and plasma states whose properties are quite different from molecular hydrogen. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound As a plasma, hydrogen's electron and proton are not bound together, resulting in very high electrical conductivity and high emissivity (producing the light from the sun and other stars). The charged particles are highly influenced by magnetic and electric fields. For example, in the solar wind they interact with the Earth's magnetosphere giving rise to Birkeland currents and the aurora. The solar wind is a Stream of charged particles&mdasha plasma &mdashthat are ejected from the upper atmosphere of the Sun. A magnetosphere' is a highly magnetized region around and possessed by an Astronomical object. A Birkeland current is a specific magnetic field aligned current in the Earth’s Magnetosphere which flows from the Magnetotail towards the Earth on the dawn side Hydrogen is found in the neutral atomic state in the Interstellar medium. The large amount of neutral hydrogen found in the damped Lyman-alpha systems is thought to dominate the cosmological baryonic density of the Universe up to redshift z=4. The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy In Physics and Astronomy, redshift occurs when Electromagnetic radiation – usually Visible light – emitted or reflected by ^[54]

Under ordinary conditions on Earth, elemental hydrogen exists as the diatomic gas, H₂ (for data see table). However, hydrogen gas is very rare in the Earth's atmosphere (1 ppm by volume) because of its light weight, which enables it to escape from Earth's gravity more easily than heavier gases. "Parts-per" notation is used especially in Science and Engineering, to denote Ratios (relative proportions in measured quantities particularly There are several different processes that can lead to the escape of a planetary atmosphere. Still, hydrogen is the third most abundant element on the Earth's surface. ^[55] Most of the Earth's hydrogen is in the form of chemical compounds such as hydrocarbons and water. A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Water is a common Chemical substance that is essential for the survival of all known forms of Life. ^[33] Hydrogen gas is produced by some bacteria and algae and is a natural component of flatus. Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Flatulence is the production of a mixture of gases in the digestive tract of Mammals that are byproducts of the digestion process Methane is a hydrogen source of increasing importance. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. ^[56]

History

Discovery and use

Hydrogen gas, H₂, was first artificially produced and formally described by T. Von Hohenheim (also known as Paracelsus, 1493–1541) via the mixing of metals with strong acids. Paracelsus (11 November or 17 December 1493 in Einsiedeln Switzerland – 24 September 1541 in Salzburg, Austria) was an alchemist, The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across A Strong acid is an Acid that Ionizes completely in an Aqueous solution (not in the case of Sulfuric acid as it is diprotic ^[57] He was unaware that the flammable gas produced by this chemical reaction was a new chemical element. 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 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. In 1671, Robert Boyle rediscovered and described the reaction between iron filings and dilute acids, which results in the production of hydrogen gas. Robert Boyle was a Natural philosopher, chemist physicist inventor and early Gentleman scientist, noted for his work in Physics and Chemistry Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are ^[58] In 1766, Henry Cavendish was the first to recognize hydrogen gas as a discrete substance, by identifying the gas from a metal-acid reaction as "inflammable air" and further finding in 1781 that the gas produces water when burned. Henry Cavendish, FRS (10 October 1731 - 24 February 1810 was a British Scientist noted for his discovery of Hydrogen or what he called "inflammable 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 He is usually given credit for its discovery as an element. ^[59][60] In 1783, Antoine Lavoisier gave the element the name of hydrogen (from the Greek hydro meaning water and genes meaning creator)^[61] when he and Laplace reproduced Cavendish's finding that water is produced when hydrogen is burned. ^[60]

Hydrogen was liquefied for the first time by James Dewar in 1898 by using his invention, the vacuum flask. Sir James Dewar FRS ( September 20, 1842 &ndash March 27, 1923) was a Scottish Chemist and Physicist ^[60] He produced solid hydrogen the next year. ^[60] Deuterium was discovered in December 1931 by Harold Urey, and tritium was prepared in 1934 by Ernest Rutherford, Mark Oliphant, and Paul Harteck. Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth Harold Clayton Urey ( April 29, 1893 &ndash January 5, 1981) was an American Physical chemist whose pioneering work Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. Ernest Rutherford 1st Baron Rutherford of Nelson, OM, PC, FRS (30 August 1871 – 19 October 1937 was a New Zealand Physicist Sir Marcus 'Mark' Laurence Elwin Oliphant AC, KBE ( October 8 1901 &ndash July 14, 2000) was an Australian Paul Karl Maria Harteck ( 20 July 1902 in Vienna, Austria &ndash 22 January 1985 in Santa Barbara, California ^[59] Heavy water, which consists of deuterium in the place of regular hydrogen, was discovered by Urey's group in 1932. Heavy water is water which contains a higher proportion than normal of the Isotope Deuterium, as deuterium oxide, D2O or ²H2O ^[60] One of the first uses of H₂ was for limelight. Limelight is a type of Stage lighting once used in Theatres and Music halls An intense illumination is created when an oxyhydrogen flame is directed ^[60]

The first hydrogen-filled balloon was invented by Jacques Charles in 1783. A balloon is a flexible bag filled with a type of Gas, such as Helium, Hydrogen, Nitrous oxide or air. Jacques Alexandre César Charles ( November 12, 1746 – April 7, 1823) was a French inventor scientist mathematician and balloonist ^[60] Hydrogen provided the lift for the first reliable form of air-travel following the 1852 invention of the first hydrogen-lifted airship by Henri Giffard. Henri Giffard (1825-1882 was a French engineer Giffard invented the Injector and the powered Airship with a steam engine weighing over 400 lb it was the world's ^[60] German count Ferdinand von Zeppelin promoted the idea of rigid airships lifted by hydrogen that later were called Zeppelins; the first of which had its maiden flight in 1900. Ferdinand Adolf August Heinrich Graf von Zeppelin mostly called Count Zeppelin) ( July 8, 1838 – March 8, 1917) was a A Zeppelin is a type of Rigid airship pioneered by the German Count Ferdinand von Zeppelin in the early 20th century based on designs he had outlined ^[60] Regularly-scheduled flights started in 1910 and by the outbreak of World War I in August 1914 they had carried 35,000 passengers without a serious incident. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All Hydrogen-lifted airships were used as observation platforms and bombers during the war.

The first non-stop transatlantic crossing was made by the British airship R34 in 1919. Regular passenger service resumed in the 1920s and the discovery of helium reserves in the United States promised increased safety, but the U. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical The United States of America —commonly referred to as the S. government refused to sell the gas for this purpose. Therefore, H₂ was used in the Hindenburg airship, which was destroyed in a midair fire over New Jersey on 6 May 1937. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout New Jersey ( is a state in the Mid-Atlantic and Northeastern regions of the United States. Events 1527 - Spanish and German troops sack Rome; some consider this the end of the Renaissance. Year 1937 ( MCMXXXVII) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar. ^[60] The incident was broadcast live on radio and filmed. Ignition of leaking hydrogen as widely assumed to be the cause but later investigations pointed to ignition of the aluminumized fabric coating by static electricity. WikipediaNaming For the science of static charges see Electrostatics Static electricity refers to the accumulation of excess Electric charge in a But the damage to hydrogen's reputation as a lifting gas was already done.

Role in quantum theory

Hydrogen emission spectrum

Because of its relatively simple atomic structure, consisting only of a proton and an electron, the hydrogen atom, together with the spectrum of light produced from it or absorbed by it, has been central to the development of the theory of atomic structure. A hydrogen atom is an atom of the chemical element Hydrogen. The electrically neutral History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny ^[62] Furthermore, the corresponding simplicity of the hydrogen molecule and the corresponding cation H₂⁺ allowed fuller understanding of the nature of the chemical bond, which followed shortly after the quantum mechanical treatment of the hydrogen atom had been developed in the mid-1920s. A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic

One of the first quantum effects to be explicitly noticed (but not understood at the time) was a Maxwell observation involving hydrogen, half a century before full quantum mechanical theory arrived. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Maxwell observed that the specific heat capacity of H₂ unaccountably departs from that of a diatomic gas below room temperature and begins to increasingly resemble that of a monatomic gas at cryogenic temperatures. Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the Temperature of a unit quantity Diatomic molecules are molecules made only of two Atoms of either the same or different Chemical elements The prefix di- means two in Greek According to quantum theory, this behavior arises from the spacing of the (quantized) rotational energy levels, which are particularly wide-spaced in H₂ because of its low mass. These widely spaced levels inhibit equal partition of heat energy into rotational motion in hydrogen at low temperatures. Diatomic gases composed of heavier atoms do not have such widely spaced levels and do not exhibit the same effect. ^[63]

Production

For more details on this topic, see Hydrogen production. Hydrogen is commonly produced by extraction from Hydrocarbon Fossil fuels via a chemical path

H₂ is produced in chemistry and biology laboratories, often as a by-product of other reactions; in industry for the hydrogenation of unsaturated substrates; and in nature as a means of expelling reducing equivalents in biochemical reactions. Hydrogenation is the Chemical reaction that results in addition of Hydrogen (H2 Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state

Laboratory

In the laboratory, H₂ is usually prepared by the reaction of acids on metals such as zinc. A laboratory (informally lab) is a facility that provides controlled conditions in which scientific Research, Experiments and Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30

Zn + 2 H⁺ → Zn²⁺ + H₂

Aluminium produces H₂ upon treatment with acids but also with base:

2 Al + 6 H₂O → 2 Al(OH)₃ + 3 H₂

The electrolysis of water is a simple method of producing hydrogen. Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 WikipediaNaming In chemistry and manufacturing electrolysis is a method of separating chemically bonded elements and compounds by passing an Electric current A low voltage current is run through the water, and gaseous oxygen forms at the anode while gaseous hydrogen forms at the cathode. An anode is an Electrode through which Electric current flows into a polarized electrical device A cathode is an Electrode through which (positive Electric current flows out of a polarized electrical device Typically the cathode is made from platinum or another inert metal when producing hydrogen for storage. If, however, the gas is to be burnt on site, oxygen is desirable to assist the combustion, and so both electrodes would be made from inert metals. (Iron, for instance, would oxidize, and thus decrease the amount of oxygen given off. ) The theoretical maximum efficiency (electricity used vs. energetic value of hydrogen produced) is between 80–94%. ^[64]

2H₂O(aq) → 2H₂(g) + O₂(g)

In 2007, it was discovered that an alloy of aluminium and gallium in pellet form added to water could be used to generate hydrogen. Gallium (ˈgæliəm is a Chemical element that has the symbol Ga and Atomic number 31 The process also creates alumina, but the expensive gallium, which prevents the formation of an oxide skin on the pellets, can be re-used. This has important potential implications for a hydrogen economy, since hydrogen can be produced on-site and does not need to be transported. ^[65]

Industrial

Hydrogen can be prepared in several different ways, but economically the most important processes involve removal of hydrogen from hydrocarbons. Commercial bulk hydrogen is usually produced by the steam reforming of natural gas. Steam reforming (SR hydrogen reforming or catalytic oxidation, is a method of producing Hydrogen from Hydrocarbons. Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, ^[66] At high temperatures (700–1100 °C; 1,300–2,000 °F), steam (water vapor) reacts with methane to yield carbon monoxide and H₂. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas.

CH₄ + H₂O → CO + 3 H₂

This reaction is favored at low pressures but is nonetheless conducted at high pressures (20 atm; 600 inHg) since high pressure H₂ is the most marketable product. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Inches of mercury, inHg or "Hg is a measuring unit for Pressure. The product mixture is known as "synthesis gas" because it is often used directly for the production of methanol and related compounds. Syngas (from syn thesis gas) is the name given to a gas mixture that contains varying amounts of Carbon monoxide and Hydrogen. Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a Chemical compound Hydrocarbons other than methane can be used to produce synthesis gas with varying product ratios. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. One of the many complications to this highly optimized technology is the formation of coke or carbon:

CH₄ → C + 2 H₂

Consequently, steam reforming typically employs an excess of H₂O. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Additional hydrogen can be recovered from the steam by use of carbon monoxide through the water gas shift reaction, especially with an iron oxide catalyst. The water gas shift reaction (WGS is a Chemical reaction in which Carbon monoxide reacts with Water to form Carbon dioxide and Hydrogen Altogether there are sixteen known Iron Oxides and oxyhydroxides This reaction is also a common industrial source of carbon dioxide:^[66]

CO + H₂O → CO₂ + H₂

Other important methods for H₂ production include partial oxidation of hydrocarbons:^[67]

2 CH₄ + O₂ → 2 CO + 4 H₂

and the coal reaction, which can serve as a prelude to the shift reaction above:^[66]

C + H₂O → CO + H₂

Hydrogen is sometimes produced and consumed in the same industrial process, without being separated. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single In the Haber process for the production of ammonia, hydrogen is generated from natural gas. The Haber process, also called the Haber–Bosch process, is the Nitrogen fixation reaction of Nitrogen and Hydrogen, over an iron substrate Because of its many uses Ammonia is one of the most highly-produced inorganic chemicals ^[68] Electrolysis of brine to yield chlorine also produces hydrogen as a co-product. In chemistry and manufacturing electrolysis is a method of separating chemically bonded elements and compounds by passing an Electric current Brine (lat saltus) is Water saturated or nearly saturated with Salt (NaCl Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and ^[69]

Solar Thermochemical

A number of laboratories (including in France, Germany, Greece, Japan, and the USA) are developing thermo chemical methods to produce hydrogen from solar energy and water. ^[70]

Applications

Large quantities of H₂ are needed in the petroleum and chemical industries. The largest application of H₂ is for the processing ("upgrading") of fossil fuels, and in the production of ammonia. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor The key consumers of H₂ in the petrochemical plant include hydrodealkylation, hydrodesulfurization, and hydrocracking. Hydrodealkylation is a chemical reaction that often involves reacting an Aromatic hydrocarbon, such as Toluene, in the presence of Hydrogen gas to form Hydrodesulfurization (HDS is a Catalytic chemical process widely used to remove Sulfur (S from Natural gas and from refined petroleum products In Petroleum geology and Chemistry, cracking is the process whereby complex organic Molecules such as Kerogens or heavy Hydrocarbons H₂ has several other important uses. H₂ is used as a hydrogenating agent, particularly in increasing the level of saturation of unsaturated fats and oils (found in items such as margarine), and in the production of methanol. Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a Chemical compound It is similarly the source of hydrogen in the manufacture of hydrochloric acid. Hydrochloric acid is the Solution of Hydrogen chloride ( H[[Chlorine Cl]] in water H₂ is also used as a reducing agent of metallic ores. A reducing agent (also called a reductant or reducer) is the element or a compound in a Redox (reduction-oxidation reaction (see Electrochemistry An ore is a volume of rock containing components or Minerals in a mode of occurrence that renders it valuable for mining ^[71]

Apart from its use as a reactant, H₂ has wide applications in physics and engineering. It is used as a shielding gas in welding methods such as atomic hydrogen welding. Shielding gases are inert or semi- Inert gases that are commonly used in several Welding processes most notably Gas metal arc welding and Gas tungsten Welding is a fabrication process that joins materials usually Metals or Thermoplastics by causing coalescence. ^[72][73] H₂ is used as the rotor coolant in electrical generators at power stations, because it has the highest thermal conductivity of any gas. In Electricity generation, an electrical generator is a device that converts Mechanical energy to Electrical energy, generally using Electromagnetic A power station (also referred to as generating station, power plant or powerhouse) is an industrial facility for the generation of In Physics, thermal conductivity, k is the property of a material that indicates its ability to conduct Heat. Liquid H₂ is used in cryogenic research, including superconductivity studies. Cryogenics is often used incorrectly to refer to Cryonics, cryopreserving humans or animals Superconductivity is a phenomenon occurring in certain Materials generally at very low Temperatures characterized by exactly zero electrical resistance ^[74] Since H₂ is lighter than air, having a little more than 1/15th of the density of air, it was once widely used as a lifting agent in balloons and airships. Terminology In some countries airships are also known as dirigibles from the French (fr ''diriger'' to direct plus -ible) meaning "directable" ^[75]

In more recent applications, hydrogen is used pure or mixed with nitrogen (sometimes called forming gas) as a tracer gas for minute leak detection. Forming gas is a mixture of up to 10% Hydrogen in Nitrogen. It is sometimes called a "dissociated Ammonia atomosphere" due to the reaction which Applications can be found in the automotive, chemical, power generation, aerospace, and telecommunications industries. ^[76] Hydrogen is an authorized food additive (E 949) that allows food package leak testing among other anti-oxidizing properties. ^[77]

Hydrogen's rarer isotopes also each have specific applications. Deuterium (hydrogen-2) is used in nuclear fission applications as a moderator to slow neutrons, and in nuclear fusion reactions. Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth The CANDU reactor is a Canadian-invented Pressurized heavy water reactor developed initially in the late 1950s and 1960s by a partnership between Atomic Energy of In Nuclear engineering, a neutron moderator is a medium which reduces the velocity of Fast neutrons thereby turning them into Thermal neutrons capable This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus ^[60] Deuterium compounds have applications in chemistry and biology in studies of reaction isotope effects. The kinetic isotope effect ( KIE) is a variation in the Reaction rate of a Chemical reaction when an Atom in one of the reactants is replaced ^[78] Tritium (hydrogen-3), produced in nuclear reactors, is used in the production of hydrogen bombs,^[79] as an isotopic label in the biosciences,^[49] and as a radiation source in luminous paints. Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. This article is a subarticle of Nuclear power. A nuclear reactor is a device in which Nuclear chain reactions are initiated controlled The Teller–Ulam design is a Nuclear weapon design which is used in Megaton -range Thermonuclear weapons and is more colloquially referred to as "the Beta particles are high-energy high-speed Electrons or Positrons emitted by certain types of Radioactive nuclei such as Potassium -40 ^[80]

The triple point temperature of equilibrium hydrogen is a defining fixed point on the ITS-90 temperature scale at 13. In Thermodynamics, the triple point of a substance is the Temperature and Pressure at which three phases (for example Gas, Liquid The International Temperature Scale of 1990 ( ITS-90) is an equipment calibration standard for making measurements on the Kelvin and 8033 kelvins. 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 ^[81]

Energy carrier

See also: Hydrogen economy and hydrogen infrastructure

Hydrogen is not an energy source,^[82] except in the hypothetical context of commercial nuclear fusion power plants using deuterium or tritium, a technology presently far from development. The hydrogen economy is a proposed method of deriving the Energy needed for Motive power (cars boats airplanes buildings or portable electronics by reacting A hydrogen infrastructure is composed of the structural elements that provide the framework supporting the hydrogen fueling infrastructure In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus 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. ^[83] The Sun's energy comes from nuclear fusion of hydrogen, but this process is difficult to achieve controllably on Earth. ^[84] Elemental hydrogen from solar, biological, or electrical sources costs more in energy to make than is obtained by burning it. Hydrogen may be obtained from fossil sources (such as methane) for less energy than required to make it, but these sources are unsustainable, and are also themselves direct energy sources. ^[82]

The energy density per unit volume of both liquid hydrogen and hydrogen gas at any practicable pressure is significantly less than that of traditional fuel sources, although the energy density per unit fuel mass is higher. Energy density is the amount of Energy stored in a given system or region of space per unit Volume, or per unit Mass, depending on the context although ^[82] Nevertheless, elemental hydrogen has been widely discussed in the context of energy, as a possible future carrier of energy on an economy-wide scale. ^[85] For example, CO₂ sequestration followed by carbon capture and storage could be conducted at the point of H₂ production from fossil fuels. CO2 sequestration or "storage" is the storage of carbon dioxide (usually captured from the "atmosphere" in a solid material through biological or physical Carbon capture and storage ( CCS) is an approach to mitigating Global warming based on capturing Carbon dioxide (CO2 from large ^[86] Hydrogen used in transportation would burn relatively cleanly, with some NOx emissions,^[87] but without carbon emissions. The term nitrogen oxide typically refers to any Binary compound of Oxygen and Nitrogen, or to a mixture of such compounds Nitric ^[86] However, the infrastructure costs associated with full conversion to a hydrogen economy would be substantial. ^[88]

Biological reactions

For more details on this topic, see biohydrogen. Biohydrogen is Hydrogen produced via Biological processes Fermentation Biohydrogen gas can be extracted from Biomass through Dark fermentation

H₂ is a product of some types of anaerobic metabolism and is produced by several microorganisms, usually via reactions catalyzed by iron- or nickel-containing enzymes called hydrogenases. Fermentation is the process of deriving energy from the oxidation of organic compounds such as carbohydrates using an endogenous electron acceptor which is A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst 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 Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins A hydrogenase is an Enzyme that catalyses the reversible oxidation of molecular Hydrogen (H2 These enzymes catalyze the reversible redox reaction between H₂ and its component two protons and two electrons. Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Creation of hydrogen gas occurs in the transfer of reducing equivalents produced during pyruvate fermentation to water. Pyruvic acid (CH3COCO2H is an alpha-keto acid. The Carboxylate Anion of pyruvic acid is known as pyruvate. Fermentation is the process of deriving energy from the oxidation of organic compounds such as carbohydrates using an endogenous electron acceptor which is ^[89]

Water splitting, in which water is decomposed into its component protons, electrons, and oxygen, occurs in the light reactions in all photosynthetic organisms. Water splitting is the general term for a Chemical reaction in which Water is converted into Oxygen and Hydrogen. The initial stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into Potential energy. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Some such organisms—including the alga Chlamydomonas reinhardtii and cyanobacteria—have evolved a second step in the dark reactions in which protons and electrons are reduced to form H₂ gas by specialized hydrogenases in the chloroplast. Chlamydomonas reinhardtii is a motile single celled Green alga about 10 Micrometres in diameter that swims with two Flagella. Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of Bacteria that obtain their energy In Photosynthesis, the light-independent reactions, also somewhat misleadingly called the dark reactions (they don't require darkness but they require the Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. ^[90] Efforts have been undertaken to genetically modify cyanobacterial hydrogenases to efficiently synthesize H₂ gas even in the presence of oxygen. ^[91] Efforts have also been undertaken with genetically modified alga in a bioreactor. Biological hydrogen production is done in a Bioreactor based on the production of hydrogen by Algae. ^[92]

Safety and precautions

Hydrogen poses a number of hazards to human safety, from potential detonations and fires when mixed with air to being an asphyxant in its pure, oxygen-free form. Detonation is a process of Supersonic Combustion in which a Shock wave is propagated forward due to energy release in a reaction zone behind it Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the ^[93] In addition, liquid hydrogen is a cryogen and presents dangers (such as frostbite) associated with very cold liquids. Liquid hydrogen (LH2 or LH2 is the Liquid state of the element Hydrogen. Cryogenics is often used incorrectly to refer to Cryonics, cryopreserving humans or animals Frostbite ( congelatio in Medical terminology) is the Medical condition whereby damage is caused to Skin and other tissues ^[94] Hydrogen dissolves in some metals, and, in addition to leaking out, may have adverse effects on them, such as hydrogen embrittlement. Hydrogen embrittlement (or hydrogen grooving) is the process by which various metals most importantly high-strength Steel, become brittle and crack following exposure ^[95] Hydrogen gas leaking into external air may spontaneously ignite. Moreover, hydrogen fire, while being extremely hot, is almost invisible, and thus can lead to accidental burns. An accident is a specific identifiable unexpected unusual and unintended external event which occurs in a particular time and place without apparent or deliberate A burn is a type of Injury that may be caused by Heat, cold, Electricity, Chemicals, Light, Radiation, or ^[96]

Even interpreting the hydrogen data (including safety data) is confounded by a number of phenomena. Many physical and chemical properties of hydrogen depend on the parahydrogen/orthohydrogen ratio (it often takes days or weeks at a given temperature to reach the equilibrium ratio, for which the data is usually given). Each Hydrogen Molecule (H2 consists of two Hydrogen atoms linked by a Covalent bond. Hydrogen detonation parameters, such as critical detonation pressure and temperature, strongly depend on the container geometry. ^[93]

See also

References

Further reading

• (1989). "Chart of the Nuclides". Fourteenth Edition. . General Electric Company
• Ferreira-Aparicio, P; M. J. Benito, J. L. Sanz (2005). "New Trends in Reforming Technologies: from Hydrogen Industrial Plants to Multifuel Microreformers". Catalysis Reviews 47: 491–588. doi:10.1080/01614940500364958. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
• Newton, David E. (1994). The Chemical Elements. New York, NY: Franklin Watts. ISBN 0-531-12501-7.  
• Rigden, John S. (2002). Hydrogen: The Essential Element. Cambridge, MA: Harvard University Press. ISBN 0-531-12501-7.  
• Romm, Joseph, J. (2004). The Hype about Hydrogen, Fact and Fiction in the Race to Save the Climate. The Hype about Hydrogen Fact and Fiction in the Race to Save the Climate is a book by Joseph J Island Press. ISBN 1-55963-703-X.   Author interview at Global Public Media.
• Stwertka, Albert (2002). A Guide to the Elements. New York, NY: Oxford University Press. ISBN 0-19-515027-9.  

External links

• The Truth About Hydrogen; Popular Mechanics
• Basic Hydrogen Calculations of Quantum Mechanics
• National Hydrogen Association
• Hydrogen phase diagram
• RIKEN Beam Science Laboratory, Japan — Heavy hydrogen research
• Wavefunction of hydrogen
• Zinc Powder Will Drive your Hydrogen Car