Full configuration
1s² 2s² 2p⁴
In the short form, [He] stands for the 2 electrons of helium, the noble gas before oxygen. 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
Oxygen has two unpaired 2p electrons. It gains two electrons to form O²⁻, which has the neon configuration.
Configuration of oxygen ions
| Ion | Configuration | Unpaired | Moment (BM) |
|---|---|---|---|
| O²⁻ | [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 |
|---|---|---|
| 5 | Boron | [He] 2s² 2p¹ |
| 6 | Carbon | [He] 2s² 2p² |
| 7 | Nitrogen | [He] 2s² 2p³ |
| 9 | Fluorine | [He] 2s² 2p⁵ |
| 10 | Neon | [He] 2s² 2p⁶ |
| 11 | Sodium | [Ne] 3s¹ |
Questions students ask
What is the electronic configuration of oxygen?
[He] 2s² 2p⁴, or in full, 1s² 2s² 2p⁴. Oxygen has atomic number 8.
How many electrons are in each shell of oxygen?
2, 6 (K, L, M, N… shells in order).
How many unpaired electrons does oxygen have?
2 in the ground state, so oxygen atoms are paramagnetic.
What is the electronic configuration of O²⁻?
[Ne], with 0 unpaired electrons.