Chlorine vs Bromine
Chlorine and Bromine 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 Bromine wears.
Side by side
| Property | Chlorine | Bromine |
|---|---|---|
| Symbol | Cl | Br |
| Atomic number (Z) | 17 | 35 |
| Atomic mass | 35.45 u | 79.904 u |
| Category | Halogen | Halogen |
| Group | 17 | 17 |
| Period | 3 | 4 |
| Phase at room temp | gas | liquid |
| Electron configuration | [Ne] 3s^2 3p^5 | [Ar] 3d^10 4s^2 4p^5 |
| Valence electrons | 7 | 7 |
| Atomic radius | 79 pm | 94 pm |
| Electronegativity | 3.16 | 2.96 |
| First ionisation energy | 1251 kJ/mol | 1140 kJ/mol |
The verdicts
- Bigger atom: Bromine — the lower an element sits in its group, the more shells it wears.
- Greedy electron-taker: Chlorine — higher electronegativity means it pulls shared electrons harder.
- Heavier: Bromine — 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.