Bromine vs Iodine
Bromine and Iodine 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 Iodine wears.
Side by side
| Property | Bromine | Iodine |
|---|---|---|
| Symbol | Br | I |
| Atomic number (Z) | 35 | 53 |
| Atomic mass | 79.904 u | 126.90 u |
| Category | Halogen | Halogen |
| Group | 17 | 17 |
| Period | 4 | 5 |
| Phase at room temp | liquid | solid |
| Electron configuration | [Ar] 3d^10 4s^2 4p^5 | [Kr] 4d^10 5s^2 5p^5 |
| Valence electrons | 7 | 7 |
| Atomic radius | 94 pm | 115 pm |
| Electronegativity | 2.96 | 2.66 |
| First ionisation energy | 1140 kJ/mol | 1008 kJ/mol |
The verdicts
- Bigger atom: Iodine — the lower an element sits in its group, the more shells it wears.
- Greedy electron-taker: Bromine — higher electronegativity means it pulls shared electrons harder.
- Heavier: Iodine — 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.