Helium
Helium (氦, symbol He) is chemical element number 2, a Noble Gas in period 1, group 18 of the periodic table, with a standard atomic weight of about 4.0026. A colorless, odorless noble gas. The second most abundant element in the observable universe.
Properties
| Atomic number | 2 |
|---|---|
| Symbol | He |
| Atomic mass | 4.0026 u |
| Category | Noble Gas |
| Period | 1 |
| Group | 18 |
| Electron configuration | 1s² |
| Electronegativity | — |
| Covalent radius | 28 pm |
| Density | 0.000179 g/cm³ |
| Melting point | 0.95 K |
| Boiling point | 4.22 K |
| Discovery | P. Janssen & N. Lockyer, 1868 |
Overview
A colorless, odorless noble gas. The second most abundant element in the observable universe. Helium (He) is a Noble Gas with atomic number 2, located in period 1, group 18. As a noble gas it has a full outer shell, is extremely unreactive, and exists as a monatomic gas at room temperature.
Its electron configuration is 1s², with 2 electrons in the outer shell. Around 25 °C it is usually a gas (a very low melting point); it melts near 0.95 K (-272.2 °C), boils near 4.22 K (-268.9 °C), has a density around 0.000179 g/cm³.
In industry and daily life it turns up in Industrial Gas and Research. It was first described by P. Janssen & N. Lockyer in 1868. See more trends in the visualization center.
Electron shells
Electrons per shell: 2
Main uses
- Industrial Gas
- Research
Hazard
Compounds containing Helium
No compounds in this knowledge base contain Helium yet.
Data sources
Atomic mass uses IUPAC (CIAAW) standard atomic weights; the covalent radius is from Cordero et al. (2008). Verify on the RSC Periodic Table, PubChem and Wikipedia. Educational reference only.