Symbol: H
Atomic number: 1
Atomic mass: 1.00794
Group: Non-Metal
CAS-number: 1333-74-0

Physical data
Other info
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He Helium To Periodic Table HeliumHe

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Physical data

Electronic data

Shells: 1
Orbitals: 1s1
Electronegativity: 2.1, 2.2
1. Ionization potential: 13.5984 eV
2. Ionization potential: -- eV
3. Ionization potential: -- eV
Oxidation states: 1, -1
Electrical conductivity: --

Thermal data

Melting point: -255.34 °C
Boiling point: -252.87 °C
Specific heat: 14.304 J/gK
Heat of fusion: 0.05868 kJ/mol
Heat of vaporization: 0.44936 kJ/mol
Thermal conductivity: 0.001815 W/cmK

Steric data

Atomic radius: 0.79 Å
Ionic radius: 1.54 Å (+1)
Covalent radius: 0.32 Å
Atomic volume: 14.4 cm³/mol
Density (293 K): 0.00008988 g/cm³
Crystal structure: hexagonal


NuclideAbundance [%]MassSpinHalflifeDecay modeDecay tree
1H 99.984 1.0078 1/2 -- --
2H 0.0156 2.0141 1 -- --
3H 0 3.016 1/2 12.3y β- View

Other info

Name origin:Greek: hydro (water) and genes (generate)
Description:Tasteless, colorless, odorless gas. The most abundant element in the universe. Tenth most abundant element in the earth's crust.
Discovered by:Henry Cavendish
Sources:Commercial quantities are produced by reacting superheated steam with methane or carbon. In lab work from reaction of metals with acid solutions or electrolysis.
Use(s):Most hydrogen is used in the production of ammonia. Also used in balloons and in metal refining. Also used as fuel in rockets. Its two heavier isotopes are: deuterium (D) and tritium (T) used respectively for nuclear fission and fusion.