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1 -hydrogenhelium


Name, symbol, number hydrogen, H, 1
Chemical seriesnonmetals
Group, period, block 11, s
Appearancecolorless gas
[[image:{{{image name}}}.jpg|125px|]] Spectral lines of hydrogen
Standard atomic weight 1.008(1)g·mol−1
Electron configuration 1s1
Electrons per shell 1
Physical properties
Density(0 °C, 101.325 kPa)
0.08988 g/L
Liquid density at m.p.0.07 (0.0763 solid)[1] g·cm−3
Melting point14.01 K
(-259.14 °C, -434.45 °F)
Boiling point20.28 K
(-252.87 °C, -423.17 °F)
Triple point13.8033 K (-259°C), 7.042 kPa
Critical point32.97 K, 1.293 MPa
Heat of fusion(H2) 0.117 kJ·mol−1
Heat of vaporization(H2) 0.904 kJ·mol−1
Heat capacity(25 °C) (H2) 28.836 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 structurehexagonal
Oxidation states1, -1
(amphoteric oxide)
Electronegativity2.20 (Pauling scale)
Ionization energies 1st: 1312.0 kJ·mol−1
Covalent radius31±5 pm
Van der Waals radius120 pm
Magnetic orderingdiamagnetic[2]
Thermal conductivity(300 K) 0.1805 W·m−1·K−1
Speed of sound(gas, 27 °C) 1310 m/s
CAS registry number1333-74-0
Selected isotopes
Main article: Isotopes of hydrogen
iso NA half-life DM DE (MeV) DP
1H 99.985% 1H is stable with 0 neutrons
2H 0.015% 2H is stable with 1 neutrons
3H trace 12.32 y β 0.01861 3He


  1. Wiberg, Egon; Wiberg, Nils; Holleman, Arnold Frederick (2001). Inorganic chemistry. Academic Press. ISBN 0123526515. 
  2. "Magnetic susceptibility of the elements and inorganic compounds", CRC Handbook of Chemistry and Physics, 81st, CRC Press.