2He4.0026
Helium
Noble gas · element 2 · group 18, period 1
Quick facts
| Symbol | He |
|---|---|
| Atomic number | 2 |
| Relative atomic mass | 4.0026 |
| Category | Noble gas |
| Position | group 18, period 1 |
| State at 20 °C | Gas |
| Melting point | — |
| Boiling point | -268.9 °C |
| Density | 0 g/cm³ |
| Electronegativity | — |
| Electron configuration | 1s2 |
About Helium
Helium has the symbol He and atomic number 2, which means every helium atom has 2 protons in its nucleus and, in a neutral atom, 2 electrons. At room temperature it is a gas.
Noble gases are in group 0. They have a full outer shell of electrons, so they are very unreactive and exist as single atoms.
Explore it
See where helium sits, and drag the temperature slider to watch it melt and boil, on the interactive periodic table. Practise with quizzes on OmniEx.