Full configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁵
In the short form, [Kr] stands for the 36 electrons of krypton, the noble gas before iodine. 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
Iodine is in group 17, period 5, in the p-block. It has 1 unpaired electron in the ground state, so the atom is paramagnetic.
Configuration of iodine ions
| Ion | Configuration | Unpaired | Moment (BM) |
|---|---|---|---|
| I⁻ | [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 |
|---|---|---|
| 50 | Tin | [Kr] 4d¹⁰ 5s² 5p² |
| 51 | Antimony | [Kr] 4d¹⁰ 5s² 5p³ |
| 52 | Tellurium | [Kr] 4d¹⁰ 5s² 5p⁴ |
| 54 | Xenon | [Kr] 4d¹⁰ 5s² 5p⁶ |
| 55 | Caesium | [Xe] 6s¹ |
| 56 | Barium | [Xe] 6s² |
Questions students ask
What is the electronic configuration of iodine?
[Kr] 4d¹⁰ 5s² 5p⁵, or in full, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁵. Iodine has atomic number 53.
How many electrons are in each shell of iodine?
2, 8, 18, 18, 7 (K, L, M, N… shells in order).
How many unpaired electrons does iodine have?
1 in the ground state, so iodine atoms are paramagnetic.
What is the electronic configuration of I⁻?
[Xe], with 0 unpaired electrons.