Full configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹ 5d¹ 6s²
In the short form, [Xe] stands for the 54 electrons of xenon, the noble gas before cerium. Only the electrons after it are written out.
Orbital diagram
Outer subshells only. Each box is an orbital; electrons fill singly first (Hund's rule), then pair up with opposite spins.
Why it's an exception
Cerium puts one electron in 5d alongside 4f¹, because 4f and 5d are very close in energy at the start of the lanthanoids. Ce⁴⁺ has the xenon configuration, which is why cerium(IV) is a common oxidising agent.
Configuration of cerium ions
| Ion | Configuration | Unpaired | Moment (BM) |
|---|---|---|---|
| Ce³⁺ | [Xe] 4f¹ | 1 | 1.73 |
| Ce⁴⁺ | [Xe] | 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 |
|---|---|---|
| 55 | Caesium | [Xe] 6s¹ |
| 56 | Barium | [Xe] 6s² |
| 57 | Lanthanum | [Xe] 5d¹ 6s² |
| 59 | Praseodymium | [Xe] 4f³ 6s² |
| 60 | Neodymium | [Xe] 4f⁴ 6s² |
| 61 | Promethium | [Xe] 4f⁵ 6s² |
Questions students ask
What is the electronic configuration of cerium?
[Xe] 4f¹ 5d¹ 6s², or in full, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹ 5d¹ 6s². Cerium has atomic number 58.
How many electrons are in each shell of cerium?
2, 8, 18, 19, 9, 2 (K, L, M, N… shells in order).
How many unpaired electrons does cerium have?
2 in the ground state, so cerium atoms are paramagnetic.
What is the electronic configuration of Ce³⁺?
[Xe] 4f¹, with 1 unpaired electron.
Why is cerium an exception?
Cerium puts one electron in 5d alongside 4f¹, because 4f and 5d are very close in energy at the start of the lanthanoids. Ce⁴⁺ has the xenon configuration, which is why cerium(IV) is a common oxidising agent.