Argon vs Krypton
Argon and Krypton 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 Krypton wears.
Side by side
| Property | Argon | Krypton |
|---|---|---|
| Symbol | Ar | Kr |
| Atomic number (Z) | 18 | 36 |
| Atomic mass | 39.95 u | 83.798 u |
| Category | Noble gas | Noble gas |
| Group | 18 | 18 |
| Period | 3 | 4 |
| Phase at room temp | gas | gas |
| Electron configuration | [Ne] 3s^2 3p^6 | [Ar] 3d^10 4s^2 4p^6 |
| Valence electrons | 8 | 8 |
| Atomic radius | 71 pm | 88 pm |
| Electronegativity | — | 3 |
| First ionisation energy | 1521 kJ/mol | 1351 kJ/mol |
The verdicts
- Bigger atom: Krypton — the lower an element sits in its group, the more shells it wears.
- Greedy electron-taker: Krypton — higher electronegativity means it pulls shared electrons harder.
- Heavier: Krypton — 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.