Electron Configuration of Boron (B)
Boron (B, Z = 5) has the electron configuration [He] 2s^2 2p^1, filling 2 shells with 2, 3 electrons.
Teachers call it "one fact, fully handled" — exactly what this page does for Boron. 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 Boron page is one click away.
Boron: every subshell, one by one
Start from 1s and follow the running total: this is exactly how examiners expect you to build Boron's configuration on paper.
| Subshell | Electrons | Total so far |
|---|---|---|
| [He] | 0 | 2 |
| 2s | 2 | 4 |
| 2p | 1 | 5 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Boron carries 2 in shell 1, 3 in shell 2. The outermost shell holds 3 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 5 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 Boron that gives [He] 2s^2 2p^1.
Students also ask
How many electron shells does Boron have?
Boron is in period 2, so its electrons occupy 2 shells, holding 2, 3 electrons respectively.
How many valence electrons does Boron have?
Its outermost shell holds 3 electrons, so Boron has 3 valence electrons that take part in bonding.
What is the noble-gas shorthand for Boron?
The shorthand form is exactly [He] 2s^2 2p^1.