Helium (He) - Element 2 | Properties & Electron Configuration
What is Helium?
Helium (He) is element 2, a noble gas in period 1, group 18. Its electron configuration is 1s².
| Atomic Number | 2 |
| Symbol | He |
| Atomic Mass | 4.0026 u |
| Category | Noble Gas |
| Period | 1 |
| Group | 18 |
| Block | s |
| Electron Configuration | 1s² |
| Short Config | 1s² |
| Electronegativity | N/A |
| Atomic Radius | 31 pm |
| Ionization Energy | 2372 kJ/mol |
| Electron Affinity | N/A |
| Phase (STP) | Gas |
Electron Configuration
The full electron configuration of Helium is 1s². In noble gas shorthand, this is written as 1s².
Helium is a s-block element in group 18, period 1.
Periodic Trends
Atomic Radius: 31 pm. Across period 1, atomic radius generally decreases left to right as nuclear charge increases.
Ionization Energy: 2372 kJ/mol. Ionization energy generally increases across a period and decreases down a group.
View all 118 elements with trend overlays for electronegativity, atomic radius, ionization energy, and electron affinity.
Explore Helium on the Interactive Periodic Table