Atomic Properties
- Atomic Number
- 2
- Atomic Mass
- 4.0026 u
- Electron Configuration
- 1s2
- Electronegativity
- —
- Block
- s-block
- Group
- 18
- Period
- 1
Physical Properties
- Phase (STP)
- gas
- Melting Point
- 0.95 K
- Boiling Point
- 4.22 K
- Density
- 0.0002 g/cm³
About Helium
Second lightest element; inert noble gas; used in balloons and cryogenics.
Isotopes of Helium
Helium has 2 naturally occurring isotopes.
| Isotope | Mass Number | Atomic Mass (u) | Abundance | Type |
|---|---|---|---|---|
| 3He | 3 | 3.01602932 | 1.34e-4% | Stable |
| 4He | 4 | 4.002603254 | 100.00% | Stable |
Data source: NIH PubChem (aggregated from IUPAC, NIST)