Electron Configuration of Bromine (Br)
Bromine (Br, Z = 35) has the electron configuration [Ar] 3d^10 4s^2 4p^5, filling 4 shells with 2, 8, 18, 7 electrons.
Teachers call it "one fact, fully handled" — exactly what this page does for Bromine. The answer sits at the top in bold; scroll for the working, the shell-by-shell breakdown and the two questions students ask most. Need the whole picture instead — history, characteristics, uses, exam questions? The full Bromine page is one click away.
Bromine: every subshell, one by one
Start from 1s and follow the running total: this is exactly how examiners expect you to build Bromine's configuration on paper.
| Subshell | Electrons | Total so far |
|---|---|---|
| [Ar] | 0 | 18 |
| 3d | 10 | 28 |
| 4s | 2 | 30 |
| 4p | 5 | 35 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Bromine carries 2 in shell 1, 8 in shell 2, 18 in shell 3, 7 in shell 4. The outermost shell holds 7 electrons — the ones that do all the bonding.
How to derive it yourself
Follow the aufbau order (1s → 2s → 2p → 3s → 3p → 4s → 3d → …), pouring 35 electrons into orbitals of capacity 2 (s), 6 (p), 10 (d) and 14 (f) until none remain. Write the filled inner shells as the nearest noble-gas core — for Bromine that gives [Ar] 3d^10 4s^2 4p^5.
Students also ask
How many electron shells does Bromine have?
Bromine is in period 4, so its electrons occupy 4 shells, holding 2, 8, 18, 7 electrons respectively.
How many valence electrons does Bromine have?
Its outermost shell holds 7 electrons, so Bromine has 7 valence electrons that take part in bonding.
What is the noble-gas shorthand for Bromine?
The shorthand form is exactly [Ar] 3d^10 4s^2 4p^5.