Hydrogen

Atomic properties
Atomic number	1
Standard atomic weight	1.007 94(7)
Electron configuration	1s1
Physical properties
Melting point	13.957 K (−259.193 °C)
Boiling point	20.39 K (−252.76 °C)
Critical point	33.18 K, 13.00(1) bar
Ionization energy
	13.598 eV; 2178.6 kJ mol−1
Thermodynamic properties
Standard entropy	130.680(3) J K−1 mol−1
Enthalpy change of atomization	217.998(6) kJ mol−1
Entropy change of atomization	114.717(2) J K−1 mol−1
Enthalpy change of vaporization	0.904 kJ mol−1
Hazards
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H220
Miscellaneous
CAS number	1333-74-0
EC number	215-605-7
	Where appropriate, and unless otherwise stated, data are given for 100 kPa (1 bar) and 298.15 K (25 °C).
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– ← hydrogen → helium

–
↑
H
↓
Li

Hydrogen (symbol: H) is a chemical element, the most abundant element in the universe.

References

↑ Hydrogen. In NIST Chemistry WebBook; National Institute for Standards and Technology, <http://webbook.nist.gov/cgi/inchi/InChI%3D1S/H2/h1H>. (accessed 20 June 2010).
↑ ^2.0 ^2.1 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 38–74. ISBN 0-08-022057-6.
↑ CRC Handbook of Chemistry and Physics, 62nd ed.; Weast, Robert C., Ed.; CRC Press: Boca Raton, FL, 1981; p E-65. ISBN 0-8493-0462-8.
↑ Cox, J. D.; Wagman, D. D.; Medvedev, V. A. CODATA Key Values for Thermodynamics; Hemisphere: New York, 1989. ISBN 0891167587, <http://www.codata.org/resources/databases/key1.html>.
↑ Index no. 001-001-00-9 of Annex VI, Part 3, to Regulation (EC) No 1272/2008 of the European Parliament and of the Council of 16 December 2008 on classification, labelling and packaging of substances and mixtures, amending and repealing Directives 67/548/EEC and 1999/45/EC, and amending Regulation (EC) No 1907/2006. OJEU L353, 31.12.2008, pp 1–1355 at p 340.

See also the corresponding article on Wikipedia.

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