Hydrogen

  • hydrogen, 1h
    hydrogen discharge tube.jpg
    purple glow in its plasma state
    hydrogen
    appearancecolorless gas
    standard atomic weight ar, std(h)[1.007841.00811] conventional: 1.008
    hydrogen in the periodic table
    hydrogen helium
    lithium beryllium boron carbon nitrogen oxygen fluorine neon
    sodium magnesium aluminium silicon phosphorus sulfur chlorine argon
    potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton
    rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon
    caesium barium lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury (element) thallium lead bismuth polonium astatine radon
    francium radium actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium nihonium flerovium moscovium livermorium tennessine oganesson


    h

    li
    – ← hydrogenhelium
    atomic number (z)1
    group1: h and alkali metals
    periodperiod 1
    blocks-block
    element category  reactive nonmetal
    electron configuration1s1
    electrons per shell1
    physical properties
    phase at stpgas
    melting point(h2) 13.99 k ​(−259.16 °c, ​−434.49 °f)
    boiling point(h2) 20.271 k ​(−252.879 °c, ​−423.182 °f)
    density (at stp)0.08988 g/l
    when liquid (at m.p.)0.07 g/cm3 (solid: 0.0763 g/cm3)[1]
    when liquid (at b.p.)0.07099 g/cm3
    triple point13.8033 k, ​7.041 kpa
    critical point32.938 k, 1.2858 mpa
    heat of fusion(h2) 0.117 kj/mol
    heat of vaporization(h2) 0.904 kj/mol
    molar heat capacity(h2) 28.836 j/(mol·k)
    vapor pressure
    p (pa) 1 10 100 1 k 10 k 100 k
    at t (k) 15 20
    atomic properties
    oxidation states−1, +1 (an amphoteric oxide)
    electronegativitypauling scale: 2.20
    ionization energies
    • 1st: 1312.0 kj/mol
    covalent radius31±5 pm
    van der waals radius120 pm
    color lines in a spectral range
    spectral lines of hydrogen
    other properties
    natural occurrenceprimordial
    crystal structurehexagonal
    hexagonal crystal structure for hydrogen
    speed of sound1310 m/s (gas, 27 °c)
    thermal conductivity0.1805 w/(m·k)
    magnetic orderingdiamagnetic[2]
    magnetic susceptibility−3.98·10−6 cm3/mol (298 k)[3]
    cas number12385-13-6
    1333-74-0 (h2)
    history
    discoveryhenry cavendish[4][5] (1766)
    named byantoine lavoisier[6] (1783)
    main isotopes of hydrogen
    iso­tope abun­dance half-life (t1/2) decay mode pro­duct
    1h 99.98% stable
    2h 0.02% stable
    3h trace 12.32 y β 3he
    | references

    hydrogen is the chemical element with the symbol h and atomic number 1. with a standard atomic weight of 1.008, hydrogen is the lightest element in the periodic table. hydrogen is the most abundant chemical substance in the universe, constituting roughly 75% of all baryonic mass.[7][note 1] non-remnant stars are mainly composed of hydrogen in the plasma state. the most common isotope of hydrogen, termed protium (name rarely used, symbol 1h), has one proton and no neutrons.

    the universal emergence of atomic hydrogen first occurred during the recombination epoch (big bang). at standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula h2. since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on earth exists in molecular forms such as water or organic compounds. hydrogen plays a particularly important role in acid–base reactions because most acid-base reactions involve the exchange of protons between soluble molecules. in ionic compounds, hydrogen can take the form of a negative charge (i.e., anion) when it is known as a hydride, or as a positively charged (i.e., cation) species denoted by the symbol h+. the hydrogen cation is written as though composed of a bare proton, but in reality, hydrogen cations in ionic compounds are always more complex. as the only neutral atom for which the schrödinger equation can be solved analytically,[8] study of the energetics and bonding of the hydrogen atom has played a key role in the development of quantum mechanics.

    hydrogen gas was first artificially produced in the early 16th century by the reaction of acids on metals. in 1766–81, henry cavendish was the first to recognize that hydrogen gas was a discrete substance,[9] and that it produces water when burned, the property for which it was later named: in greek, hydrogen means "water-former".

    industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water.[10] most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing (e.g., hydrocracking) and ammonia production, mostly for the fertilizer market. hydrogen is problematic in metallurgy because it can embrittle many metals,[11] complicating the design of pipelines and storage tanks.[12]

  • properties
  • history
  • cosmic prevalence and distribution
  • production
  • applications
  • biological reactions
  • safety and precautions
  • notes
  • references
  • further reading
  • external links

Hydrogen, 1H
Hydrogen discharge tube.jpg
Purple glow in its plasma state
Hydrogen
Appearancecolorless gas
Standard atomic weight Ar, std(H)[1.007841.00811] conventional: 1.008
Hydrogen in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson


H

Li
– ← hydrogenhelium
Atomic number (Z)1
Group1: H and alkali metals
Periodperiod 1
Blocks-block
Element category  Reactive nonmetal
Electron configuration1s1
Electrons per shell1
Physical properties
Phase at STPgas
Melting point(H2) 13.99 K ​(−259.16 °C, ​−434.49 °F)
Boiling point(H2) 20.271 K ​(−252.879 °C, ​−423.182 °F)
Density (at STP)0.08988 g/L
when liquid (at m.p.)0.07 g/cm3 (solid: 0.0763 g/cm3)[1]
when liquid (at b.p.)0.07099 g/cm3
Triple point13.8033 K, ​7.041 kPa
Critical point32.938 K, 1.2858 MPa
Heat of fusion(H2) 0.117 kJ/mol
Heat of vaporization(H2) 0.904 kJ/mol
Molar heat capacity(H2) 28.836 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 15 20
Atomic properties
Oxidation states−1, +1 (an amphoteric oxide)
ElectronegativityPauling scale: 2.20
Ionization energies
  • 1st: 1312.0 kJ/mol
Covalent radius31±5 pm
Van der Waals radius120 pm
Color lines in a spectral range
Spectral lines of hydrogen
Other properties
Natural occurrenceprimordial
Crystal structurehexagonal
Hexagonal crystal structure for hydrogen
Speed of sound1310 m/s (gas, 27 °C)
Thermal conductivity0.1805 W/(m·K)
Magnetic orderingdiamagnetic[2]
Magnetic susceptibility−3.98·10−6 cm3/mol (298 K)[3]
CAS Number12385-13-6
1333-74-0 (H2)
History
DiscoveryHenry Cavendish[4][5] (1766)
Named byAntoine Lavoisier[6] (1783)
Main isotopes of hydrogen
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
1H 99.98% stable
2H 0.02% stable
3H trace 12.32 y β 3He
| references

Hydrogen is the chemical element with the symbol H and atomic number 1. With a standard atomic weight of 1.008, hydrogen is the lightest element in the periodic table. Hydrogen is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.[7][note 1] Non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed protium (name rarely used, symbol 1H), has one proton and no neutrons.

The universal emergence of atomic hydrogen first occurred during the recombination epoch (Big Bang). At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H2. Since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays a particularly important role in acid–base reactions because most acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a negative charge (i.e., anion) when it is known as a hydride, or as a positively charged (i.e., cation) species denoted by the symbol H+. The hydrogen cation is written as though composed of a bare proton, but in reality, hydrogen cations in ionic compounds are always more complex. As the only neutral atom for which the Schrödinger equation can be solved analytically,[8] study of the energetics and bonding of the hydrogen atom has played a key role in the development of quantum mechanics.

Hydrogen gas was first artificially produced in the early 16th century by the reaction of acids on metals. In 1766–81, Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance,[9] and that it produces water when burned, the property for which it was later named: in Greek, hydrogen means "water-former".

Industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water.[10] Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing (e.g., hydrocracking) and ammonia production, mostly for the fertilizer market. Hydrogen is problematic in metallurgy because it can embrittle many metals,[11] complicating the design of pipelines and storage tanks.[12]