Electron Configuration of Lanthanum (La)
Lanthanum (La, Z = 57) has the electron configuration [Xe] 5d¹ 6s², filling 6 shells with 2, 8, 18, 18, 9, 2 electrons.
Looking for Lanthanum'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 Lanthanum page is one click away.
Lanthanum: every subshell, one by one
Read the configuration like a receipt: each line is one subshell, and the running total climbs exactly to 57 electrons — never one more, never one less.
| Subshell | Electrons | Total so far |
|---|---|---|
| [Xe] | 0 | 54 |
| 5d | 1 | 55 |
| 6s | 2 | 57 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Lanthanum carries 2 in shell 1, 8 in shell 2, 18 in shell 3, 18 in shell 4, 9 in shell 5, 2 in shell 6. 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 57 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 Lanthanum that gives [Xe] 5d¹ 6s².
Note: Lanthanum 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 [Xe] 5d¹ 6s².
Students also ask
How many electron shells does Lanthanum have?
Lanthanum is in period 6, so its electrons occupy 6 shells, holding 2, 8, 18, 18, 9, 2 electrons respectively.
How many valence electrons does Lanthanum have?
Its outermost shell holds 2 electrons, so Lanthanum has 2 valence electrons that take part in bonding.
What is the noble-gas shorthand for Lanthanum?
The shorthand form is exactly [Xe] 5d¹ 6s².