| Atomic Number: | 2 |
| Element Symbol: | He |
| Element Name: | Helium |
| Atomic Weight: | 4.002602 |
| Group Number: | 18 |
| Group Name: | Noble gas |
| Period Number: | 1 |
| Block: | p-block |
| Ground State Configuration: | 1s2 |
| Ground State Level: | 1S0 |
| Standard State: | Gas |
| Bond Length: | 300 |
| Atomic Radius Calculated: | 31 |
| Covalent Radius Empirical: | 32 |
| Vander Waals Radius: | 140 |
| First Ionization Energy: | 2372.3 |
| Allred Rochow Electronegativity: | 5.50 |
| Mulliken Jaffe Electronegativity: | 3.49 |
| Molar Volume: | 21.0 |
| Velocity Of Sound: | 970 |
| Refractive Index: | 1.000035 (gas; liquid 1.028) |
| Melting Point: | -272.2 |
| Boiling Point: | -268.93 |
| Critical Temperature: | -267.96 |
| Thermal Conductivity: | 0.1513 |
| Enthalpy Of Fusion: | 0.02 |
| Enthalpy Of Vaporization: | 0.083 |
| Color: | Colourless |
| Classification: | Non-metallic |
| Discovered By: | Sir William Ramsay and independently by N. A. Langley and P. T. Cleve |
| Discovered At: | London, England and Uppsala, Sweden |
| Discovered When: | 1895 |
| Origin Of Name: | From the Greek word helios meaning sun |
Calculate the molecular weight of Helium or molecular weight He.
Also see the full list of chemical elements and atomic weights.