Hydrogen vs Helium
The universe’s first two elements: one bonds with almost everything, the other bonds with almost nothing.
Side by side
| Property | Hydrogen | Helium |
|---|---|---|
| Symbol | H | He |
| Atomic number (Z) | 1 | 2 |
| Atomic mass | 1.008 u | 4.0026 u |
| Category | Nonmetal | Noble gas |
| Group | 1 | 18 |
| Period | 1 | 1 |
| Phase at room temp | gas | gas |
| Electron configuration | 1s^1 | 1s^2 |
| Valence electrons | 1 | 2 |
| Atomic radius | 53 pm | 31 pm |
| Electronegativity | 2.2 | — |
| First ionisation energy | 1312 kJ/mol | 2372 kJ/mol |
The verdicts
- Bigger atom: Hydrogen — the lower an element sits in its group, the more shells it wears.
- Greedy electron-taker: Hydrogen — higher electronegativity means it pulls shared electrons harder.
- Heavier: Helium — compare the atomic masses in the table above.
Want the visual version with bars for radius, electronegativity and ionisation energy? Open the interactive compare tool with this pair already loaded.