Full configuration
1s² 2s² 2p¹
In the short form, [He] stands for the 2 electrons of helium, the noble gas before boron. Only the electrons after it are written out.
Orbital diagram
1s↑↓
2s↑↓
2p↑
Outer subshells only. Each box is an orbital; electrons fill singly first (Hund's rule), then pair up with opposite spins.
What the configuration tells you
Boron is in group 13, period 2, in the p-block. It has 1 unpaired electron in the ground state, so the atom is paramagnetic.
Configuration of boron ions
| Ion | Configuration | Unpaired | Moment (BM) |
|---|---|---|---|
| B³⁺ | 1s² | 0 | 0.00 |
Moment is the spin-only magnetic moment μ = √(n(n + 2)) Bohr magnetons, where n is the number of unpaired electrons.
Nearby elements
| Z | Element | Configuration |
|---|---|---|
| 2 | Helium | 1s² |
| 3 | Lithium | [He] 2s¹ |
| 4 | Beryllium | [He] 2s² |
| 6 | Carbon | [He] 2s² 2p² |
| 7 | Nitrogen | [He] 2s² 2p³ |
| 8 | Oxygen | [He] 2s² 2p⁴ |
Questions students ask
What is the electronic configuration of boron?
[He] 2s² 2p¹, or in full, 1s² 2s² 2p¹. Boron has atomic number 5.
How many electrons are in each shell of boron?
2, 3 (K, L, M, N… shells in order).
How many unpaired electrons does boron have?
1 in the ground state, so boron atoms are paramagnetic.
What is the electronic configuration of B³⁺?
1s², with 0 unpaired electrons.