2He4.00260
Helium
Noble Gas
Gas at STP
Period 1Group 18Block SDiscovered 1868
1s2
Helium 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.
📖 Read more on Wikipedia →Emission Spectrum
Atomic Properties
| Atomic Number | 2 |
| Atomic Mass | 4.00260 u |
| Electron Configuration | 1s2 |
| Oxidation States | 0 |
| Atomic Radius | 140 pm |
| Ionization Energy | 24.587 eV |
| Block | S |
Physical Properties
| Appearance | colorless gas, exhibiting a red-orange glow when placed in a high-voltage electric field |
| Standard State | Gas |
| Melting Point | 0.95 K (-272.2 °C) |
| Boiling Point | 4.22 K (-268.9 °C) |
| Density | 0.0001785 g/L |
| CPK Color | #D9FFFF |
Classification
| Category | Noble Gas |
| Group Block | Noble gas |
| Period | 1 |
| Group | 18 |
| Block | S |
Discovery
| Year Discovered | 1868 |
| Discovered By | Pierre Janssen |
| Electron Shells | 2 |