He
Helium
previous element
He |
|
|
Helium |
||
| previous element |
next
element |
| Atomic number | 2 |
| Atomic weight | 4.00260 |
| Orbital electronic configuration | 1s2 |
| First ionization energy (eV) | 24.587 |
| Second ionization energy (eV) | 54.416 |
| Atomic radius (Å) | 0.93 |
| Bonding radius (Å) | 0.49 |
Properties |
|
| Density (g/liter @ 0oC and 1 atm.) (gas) | 0.1787 |
| Melting point (K) | 0.95(28 atm) |
| Boiling point (K) | 4.215 |
| Heat of vaporization (kJ/mol) | 0.0845 |
| Heat of fusion (kJ/mol) | - |
| Specific heat capacity (Jg-1K-1) | 5.193 |
| Crystal structure | hexagonal |