| From Wikipedia, the free encyclopediaHelium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among all the elements. | |||||
Helium in the periodic table | |||||
|---|---|---|---|---|---|
| Symbol | He | ||||
| Atomic number | 2 | ||||
| Group | 18 | ||||
| Period | 1 | ||||
| Block | s | ||||
| Element category | Noble Gas | ||||
Physical properties | |||||
| Phase at STP | Gas | ||||
| Density | 0.1786 g/cm3 | ||||
| Atomic weight | 4.0026 u | ||||
| Melting point | 0.95 K -272.2 °C -457.96 °F | ||||
| Boiling point | 4.222 K -268.928 °C -452.0704 °F | ||||
Atomära egenskaper | |||||
| Electronegativity (Pauling Scale) | |||||
| Electron affinity | -48 kJ/mol | ||||
| Ionization energies |
| ||||
Electron configuration | |||||
| Electron configuration | 1s2 | ||||
| Electrons per shell | 2 | ||||
History | |||||
| Discovered | 1868 | ||||
| Discovered by | Pierre Janssen Norman Lockyer | ||||