Calcium vs Strontium
Calcium and Strontium 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 Strontium wears.
Side by side
| Property | Calcium | Strontium |
|---|---|---|
| Symbol | Ca | Sr |
| Atomic number (Z) | 20 | 38 |
| Atomic mass | 40.078 u | 87.62 u |
| Category | Alkaline earth metal | Alkaline earth metal |
| Group | 2 | 2 |
| Period | 4 | 5 |
| Phase at room temp | solid | solid |
| Electron configuration | [Ar] 4s^2 | [Kr] 5s^2 |
| Valence electrons | 2 | 2 |
| Atomic radius | 194 pm | 219 pm |
| Electronegativity | 1 | 0.95 |
| First ionisation energy | 590 kJ/mol | 550 kJ/mol |
The verdicts
- Bigger atom: Strontium — the lower an element sits in its group, the more shells it wears.
- Greedy electron-taker: Calcium — higher electronegativity means it pulls shared electrons harder.
- Heavier: Strontium — 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.