Full configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹
In the short form, [Xe] stands for the 54 electrons of xenon, the noble gas before caesium. 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.
What the configuration tells you
Caesium is in group 1, period 6, in the s-block. It has 1 unpaired electron in the ground state, so the atom is paramagnetic.
Configuration of caesium ions
| Ion | Configuration | Unpaired | Moment (BM) |
|---|---|---|---|
| Cs⁺ | [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 |
|---|---|---|
| 52 | Tellurium | [Kr] 4d¹⁰ 5s² 5p⁴ |
| 53 | Iodine | [Kr] 4d¹⁰ 5s² 5p⁵ |
| 54 | Xenon | [Kr] 4d¹⁰ 5s² 5p⁶ |
| 56 | Barium | [Xe] 6s² |
| 57 | Lanthanum | [Xe] 5d¹ 6s² |
| 58 | Cerium | [Xe] 4f¹ 5d¹ 6s² |
Questions students ask
What is the electronic configuration of caesium?
[Xe] 6s¹, or in full, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹. Caesium has atomic number 55.
How many electrons are in each shell of caesium?
2, 8, 18, 18, 8, 1 (K, L, M, N… shells in order).
How many unpaired electrons does caesium have?
1 in the ground state, so caesium atoms are paramagnetic.
What is the electronic configuration of Cs⁺?
[Xe], with 0 unpaired electrons.