| Atomic number | : | 2 |
| Atomic mass | : | 4.00260 g.mol-1 |
| Electronegativity according to Pauling | : | 2.1 |
| Density | : | 0.178*10-3 g.cm-3 at 20 °C |
| Melting point | : | - 272.2 (26 atm) °C |
| Boiling point | : | - 268.9 °C |
| Vanderwaals radius | : | 0.118 nm |
| Ionic radius | : | |
| Isotopes | : | 2 |
| Electronic shell | : | 1s2 |
| Energy of first ionisation | : | 2372 kJ.mol-1 |
| Discovered by | : | Sir William Ramsey in 1895 |
Atomic Structure
Uses (Balloons, deep sea diving)
