Molybdenum Electron Configuration
★ Exception to the Aufbau order. Predicted 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d4 5s2; measured 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d5 5s1.
Orbital diagram
- Valence electrons
- 6
- Unpaired electrons
- 6
- Block
- d-block
- Magnetism (atom)
- paramagnetic
Electrons per shell
| K (n = 1) | 2 |
|---|---|
| L (n = 2) | 8 |
| M (n = 3) | 18 |
| N (n = 4) | 13 |
| O (n = 5) | 1 |
Molybdenum ion configurations
| Ion | Electrons | Configuration |
|---|---|---|
| Mo6+ | 36 | [Ar] 3d10 4s2 4p6 |
How to write it
Place 42 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. Molybdenum sits in period 5, group 6, in the d-block, so its last electron enters a d subshell. Replacing the inner electrons with the previous noble gas gives the shorthand [Kr] 4d5 5s1.
Try molybdenum and its ions in the calculator, or see the full molybdenum data sheet.
Molybdenum electron configuration FAQ
What is the electron configuration of molybdenum?
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s¹. Shorthand (noble gas) notation: [Kr] 4d⁵ 5s¹.
What is the noble gas configuration of molybdenum?
[Kr] 4d⁵ 5s¹. The bracket stands for the Kr core electrons.
Why is molybdenum’s electron configuration an exception?
The simple filling (Aufbau) order predicts 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁴ 5s², but the measured ground state is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s¹. Shifting an electron gives a half-filled or filled subshell, which has extra exchange stability.
How many valence electrons does molybdenum have?
6 (1 outer s + 5 d electrons; 1 in the outermost shell).
How many unpaired electrons does molybdenum have?
6 in the ground state, following Hund’s rule. An atom with unpaired electrons is paramagnetic.
What is the electron configuration of Mo6+?
[Ar] 3d¹⁰ 4s² 4p⁶ (36 electrons). Transition metal cations lose their outer s electrons before d electrons.