Full configuration
1s² 2s² 2p⁶ 3s¹
In the short form, [Ne] stands for the 10 electrons of neon, the noble gas before sodium. Only the electrons after it are written out.
Orbital diagram
2s↑↓
2p↑↓↑↓↑↓
3s↑
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
Sodium's single 3s electron is easy to remove, which is why it forms Na⁺ so readily and reacts violently with water.
Configuration of sodium ions
| Ion | Configuration | Unpaired | Moment (BM) |
|---|---|---|---|
| Na⁺ | [Ne] | 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 |
|---|---|---|
| 8 | Oxygen | [He] 2s² 2p⁴ |
| 9 | Fluorine | [He] 2s² 2p⁵ |
| 10 | Neon | [He] 2s² 2p⁶ |
| 12 | Magnesium | [Ne] 3s² |
| 13 | Aluminium | [Ne] 3s² 3p¹ |
| 14 | Silicon | [Ne] 3s² 3p² |
Questions students ask
What is the electronic configuration of sodium?
[Ne] 3s¹, or in full, 1s² 2s² 2p⁶ 3s¹. Sodium has atomic number 11.
How many electrons are in each shell of sodium?
2, 8, 1 (K, L, M, N… shells in order).
How many unpaired electrons does sodium have?
1 in the ground state, so sodium atoms are paramagnetic.
What is the electronic configuration of Na⁺?
[Ne], with 0 unpaired electrons.