Full configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶
In the short form, [Ar] stands for the 18 electrons of argon, the noble gas before krypton. Only the electrons after it are written out.
Orbital diagram
3d↑↓↑↓↑↓↑↓↑↓
4s↑↓
4p↑↓↑↓↑↓
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
Krypton is in group 18, period 4, in the p-block. It has a full outer shell, which is why it's so unreactive.
Nearby elements
| Z | Element | Configuration |
|---|---|---|
| 33 | Arsenic | [Ar] 3d¹⁰ 4s² 4p³ |
| 34 | Selenium | [Ar] 3d¹⁰ 4s² 4p⁴ |
| 35 | Bromine | [Ar] 3d¹⁰ 4s² 4p⁵ |
| 37 | Rubidium | [Kr] 5s¹ |
| 38 | Strontium | [Kr] 5s² |
| 39 | Yttrium | [Kr] 4d¹ 5s² |
Questions students ask
What is the electronic configuration of krypton?
[Ar] 3d¹⁰ 4s² 4p⁶, or in full, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶. Krypton has atomic number 36.
How many electrons are in each shell of krypton?
2, 8, 18, 8 (K, L, M, N… shells in order).
How many unpaired electrons does krypton have?
0 in the ground state, so krypton atoms are diamagnetic.