Lanthanum Electron Configuration
★ Exception to the Aufbau order. Predicted 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f1 5s2 5p6 6s2; measured 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 5d1 6s2.
Orbital diagram
- Valence electrons
- 3
- Unpaired electrons
- 1
- Block
- f-block
- Magnetism (atom)
- paramagnetic
Electrons per shell
| K (n = 1) | 2 |
|---|---|
| L (n = 2) | 8 |
| M (n = 3) | 18 |
| N (n = 4) | 18 |
| O (n = 5) | 9 |
| P (n = 6) | 2 |
Lanthanum ion configurations
| Ion | Electrons | Configuration |
|---|---|---|
| La3+ | 54 | [Kr] 4d10 5s2 5p6 |
How to write it
Place 57 electrons into subshells in the Aufbau order (1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p), filling s with 2, p with 6, d with 10 and f with 14. Lanthanum sits in period 6, in the f-block, so its last electron enters a f subshell. Replacing the inner electrons with the previous noble gas gives the shorthand [Xe] 5d1 6s2.
Try lanthanum and its ions in the calculator, or see the full lanthanum data sheet.
Lanthanum electron configuration FAQ
What is the electron configuration of lanthanum?
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s². Shorthand (noble gas) notation: [Xe] 5d¹ 6s².
What is the noble gas configuration of lanthanum?
[Xe] 5d¹ 6s². The bracket stands for the Xe core electrons.
Why is lanthanum’s electron configuration an exception?
The simple filling (Aufbau) order predicts 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹ 5s² 5p⁶ 6s², but the measured ground state is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 5d¹ 6s². Shifting an electron gives a lower overall energy because the subshells involved are very close in energy.
How many valence electrons does lanthanum have?
3 (2 outer s + 1 d electrons; 2 in the outermost shell).
How many unpaired electrons does lanthanum have?
1 in the ground state, following Hund’s rule. An atom with unpaired electrons is paramagnetic.
What is the electron configuration of La3+?
[Kr] 4d¹⁰ 5s² 5p⁶ (54 electrons).