Atomic Mass1.0080 u

Standard StateGas

Electron Configuration1s1

Oxidation States+1, -1

Electronegativity (Pauling Scale)2.2

Atomic Radius (van der Waals)120 pm

Ionization Energy13.598 eV

Electron Affinity0.754 eV

Melting Point13.81 K

Boiling Point20.28 K

Density0.00008988 g/cm³

Year Discovered1766