Helium vs Neon
Helium and Neon sit in the same column of the periodic table — same family, one period apart — so almost every difference between them comes from one thing: the extra electron shell Neon wears.
Side by side
| Property | Helium | Neon |
|---|---|---|
| Symbol | He | Ne |
| Atomic number (Z) | 2 | 10 |
| Atomic mass | 4.0026 u | 20.180 u |
| Category | Noble gas | Noble gas |
| Group | 18 | 18 |
| Period | 1 | 2 |
| Phase at room temp | gas | gas |
| Electron configuration | 1s^2 | [He] 2s^2 2p^6 |
| Valence electrons | 2 | 8 |
| Atomic radius | 31 pm | 38 pm |
| Electronegativity | — | — |
| First ionisation energy | 2372 kJ/mol | 2081 kJ/mol |
The verdicts
- Bigger atom: Neon — the lower an element sits in its group, the more shells it wears.
- Greedy electron-taker: Helium — higher electronegativity means it pulls shared electrons harder.
- Heavier: Neon — 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.