Full configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁷ 5s¹
In the short form, [Kr] stands for the 36 electrons of krypton, the noble gas before ruthenium. Only the electrons after it are written out.
Orbital diagram
4p↑↓↑↓↑↓
4d↑↓↑↓↑↑↑
5s↑
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
Ruthenium is in group 8, period 5, in the d-block. It has 4 unpaired electrons in the ground state, so the atom is paramagnetic.
Nearby elements
| Z | Element | Configuration |
|---|---|---|
| 41 | Niobium | [Kr] 4d⁴ 5s¹ |
| 42 | Molybdenum | [Kr] 4d⁵ 5s¹ |
| 43 | Technetium | [Kr] 4d⁵ 5s² |
| 45 | Rhodium | [Kr] 4d⁸ 5s¹ |
| 46 | Palladium | [Kr] 4d¹⁰ |
| 47 | Silver | [Kr] 4d¹⁰ 5s¹ |
Questions students ask
What is the electronic configuration of ruthenium?
[Kr] 4d⁷ 5s¹, or in full, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁷ 5s¹. Ruthenium has atomic number 44.
How many electrons are in each shell of ruthenium?
2, 8, 18, 15, 1 (K, L, M, N… shells in order).
How many unpaired electrons does ruthenium have?
4 in the ground state, so ruthenium atoms are paramagnetic.
Why is ruthenium an exception?
A half-filled or completely filled subshell is extra stable, so an electron moves to reach it.