Electron Configuration of Strontium (Sr)
Strontium (Sr, Z = 38) has the electron configuration [Kr] 5s^2, filling 5 shells with 2, 8, 18, 8, 2 electrons.
Teachers call it "one fact, fully handled" — exactly what this page does for Strontium. 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 Strontium page is one click away.
Strontium: every subshell, one by one
Start from 1s and follow the running total: this is exactly how examiners expect you to build Strontium's configuration on paper.
| Subshell | Electrons | Total so far |
|---|---|---|
| [Kr] | 0 | 36 |
| 5s | 2 | 38 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Strontium carries 2 in shell 1, 8 in shell 2, 18 in shell 3, 8 in shell 4, 2 in shell 5. The outermost shell holds 2 electrons — the ones that do all the bonding.
How to derive it yourself
Follow the aufbau order (1s → 2s → 2p → 3s → 3p → 4s → 3d → …), pouring 38 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 Strontium that gives [Kr] 5s^2.
Students also ask
How many electron shells does Strontium have?
Strontium is in period 5, so its electrons occupy 5 shells, holding 2, 8, 18, 8, 2 electrons respectively.
How many valence electrons does Strontium have?
Its outermost shell holds 2 electrons, so Strontium has 2 valence electrons that take part in bonding.
What is the noble-gas shorthand for Strontium?
The shorthand form is exactly [Kr] 5s^2.