Sodium vs Potassium
Sodium and Potassium 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 Potassium wears.
Side by side
| Property | Sodium | Potassium |
|---|---|---|
| Symbol | Na | K |
| Atomic number (Z) | 11 | 19 |
| Atomic mass | 22.990 u | 39.098 u |
| Category | Alkali metal | Alkali metal |
| Group | 1 | 1 |
| Period | 3 | 4 |
| Phase at room temp | solid | solid |
| Electron configuration | [Ne] 3s^1 | [Ar] 4s^1 |
| Valence electrons | 1 | 1 |
| Atomic radius | 190 pm | 243 pm |
| Electronegativity | 0.93 | 0.82 |
| First ionisation energy | 496 kJ/mol | 419 kJ/mol |
The verdicts
- Bigger atom: Potassium — the lower an element sits in its group, the more shells it wears.
- Greedy electron-taker: Sodium — higher electronegativity means it pulls shared electrons harder.
- Heavier: Potassium — 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.