NO. 002Noble Gas

He

Helium

Helium is a colorless, odorless noble gas known for its low density and chemical inertness.

Crystal Structure

Hexagonal close-packed (hcp)

Atomic Mass4.0026 u

Density0.0001785 g/cm³

Melting Point0.95 K

Boiling Point4.22 K

Atomic Radius31 pm

Electronegativity0

Ionization Energy2372 kJ/mol

Electron Affinity0 kJ/mol

Bonding TypeCovalent

Oxidation States0

Acid/BaseNeutral

ReactivityLow

Electron Configuration

1s2

Discovered ByWilliam Ramsay

Year1895

Known Isotopes

Helium-3Helium-4