Calcium vs Iron
Calcium builds your bones; iron carries the oxygen in your blood — the two metals your body cannot live without.
Side by side
| Property | Calcium | Iron |
|---|---|---|
| Symbol | Ca | Fe |
| Atomic number (Z) | 20 | 26 |
| Atomic mass | 40.078 u | 55.845 u |
| Category | Alkaline earth metal | Transition metal |
| Group | 2 | 8 |
| Period | 4 | 4 |
| Phase at room temp | solid | solid |
| Electron configuration | [Ar] 4s^2 | [Ar] 3d^6 4s^2 |
| Valence electrons | 2 | 2 |
| Atomic radius | 194 pm | 156 pm |
| Electronegativity | 1 | 1.83 |
| First ionisation energy | 590 kJ/mol | 763 kJ/mol |
The verdicts
- Bigger atom: Calcium — the lower an element sits in its group, the more shells it wears.
- Greedy electron-taker: Iron — higher electronegativity means it pulls shared electrons harder.
- Heavier: Iron — 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.