|
|
| Helium | |
| Electron Configuration | 2 |
| Electron Configuration | 1s2 |
| Ground state | 1S0 |
| Atomic Volume | g/cm3 |
| Electronegativity | No data. |
| Magnetic ordering | No data |
| Mass magnetic susceptibility | -5.9 x 10-9 |
| Molar magnetic susceptibility | -2.36 x 10+-11 |
 Thermal Properties |
|
| Enthalpy of Atomization | No data. |
| Enthalpy of Fusion | 0.021 kJ mol-1 |
| Enthalpy of Vaporisation | 0.082 kJ mol-1 |
| Heat Capacity | 20.786 J mol-1 K-1 |
| Thermal Conductivity | 151.3 W m-1 K-1 |
| Thermal Expansion | No data. |
| Electrical Properties |
|
| Electrical resistivity | No data. |
| Electrical conductivity | No data. |
| Chemical Properties |
|
| Ionization Potential | |
 First
|
24.587 |
| Second
|
54.416 |
| Flammability |
|
| Non-flammable gas
|
| Optical Properties |
|
| Refractive Index (gas) | 1.000035 |
| Refractive Index (liquid) | 1.028 |
| Energy Levels |
|
| Kα1 (intensity 100) |
0.022 KeV |
| Atomic Radii |
|
| Empirical
|
31 pm |
| Bohr Radius
|
31 pm |
| Covalent Radius
|
32 pm |
| Van der Waals
|
140 pm |
| Triple covalent
|
No data. |
| Metallic
|
No data. |
Ionisation Energies (kJ mol-1)  |
|
| M - M+ |
2372.3 |
| M+ - M2+ |
5250.4 |
| Vapour Pressure |
||||||
| P (Pa) | 1 | 10 | 100 | 1K | 10K | 100K |
| T (K) | 3 | 4 | ||||