Electron Configuration of Ruthenium (Ru)
Ruthenium (Ru, Z = 44) has the electron configuration [Kr] 4d⁷ 5s¹, filling 5 shells with 2, 8, 18, 15, 1 electrons.
Teachers call it "one fact, fully handled" — exactly what this page does for Ruthenium. The answer sits at the top in bold; scroll for the working, the shell-by-shell breakdown and the two questions students ask most. Need the whole picture instead — history, characteristics, uses, exam questions? The full Ruthenium page is one click away.
Ruthenium: every subshell, one by one
Start from 1s and follow the running total: this is exactly how examiners expect you to build Ruthenium's configuration on paper.
| Subshell | Electrons | Total so far |
|---|---|---|
| [Kr] | 0 | 36 |
| 4d | 7 | 43 |
| 5s | 1 | 44 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Ruthenium carries 2 in shell 1, 8 in shell 2, 18 in shell 3, 15 in shell 4, 1 in shell 5. The outermost shell holds 1 electron — the ones that do all the bonding.
How to derive it yourself
Follow the aufbau order (1s → 2s → 2p → 3s → 3p → 4s → 3d → …), pouring 44 electrons into orbitals of capacity 2 (s), 6 (p), 10 (d) and 14 (f) until none remain. Write the filled inner shells as the nearest noble-gas core — for Ruthenium that gives [Kr] 4d⁷ 5s¹.
Note: Ruthenium is one of the textbook exceptions to strict aufbau filling — a half-filled or fully-filled d subshell buys extra stability, so its ground-state configuration is [Kr] 4d⁷ 5s¹.
Students also ask
How many electron shells does Ruthenium have?
Ruthenium is in period 5, so its electrons occupy 5 shells, holding 2, 8, 18, 15, 1 electrons respectively.
How many valence electrons does Ruthenium have?
Its outermost shell holds 1 electron, so Ruthenium has 1 valence electron that take part in bonding.
What is the noble-gas shorthand for Ruthenium?
The shorthand form is exactly [Kr] 4d⁷ 5s¹.