Electron Configuration of Chromium (Cr)
Chromium (Cr, Z = 24) has the electron configuration [Ar] 3d⁵ 4s¹, filling 4 shells with 2, 8, 13, 1 electrons.
Looking for Chromium's electron configuration without wading through a whole chapter? Here is the direct answer first, then the tables and derivations examiners want to see. Every number on this page comes from the same engine that powers the interactive table. Need the whole picture instead — history, characteristics, uses, exam questions? The full Chromium page is one click away.
Chromium: every subshell, one by one
Read the configuration like a receipt: each line is one subshell, and the running total climbs exactly to 24 electrons — never one more, never one less.
| Subshell | Electrons | Total so far |
|---|---|---|
| [Ar] | 0 | 18 |
| 3d | 5 | 23 |
| 4s | 1 | 24 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Chromium carries 2 in shell 1, 8 in shell 2, 13 in shell 3, 1 in shell 4. 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 24 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 Chromium that gives [Ar] 3d⁵ 4s¹.
Note: Chromium 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 [Ar] 3d⁵ 4s¹.
Students also ask
How many electron shells does Chromium have?
Chromium is in period 4, so its electrons occupy 4 shells, holding 2, 8, 13, 1 electrons respectively.
How many valence electrons does Chromium have?
Its outermost shell holds 1 electron, so Chromium has 1 valence electron that take part in bonding.
What is the noble-gas shorthand for Chromium?
The shorthand form is exactly [Ar] 3d⁵ 4s¹.