Calcium Electron Configuration
Calcium (Ca) · 20 electrons · Alkaline earth metal
1s2 2s2 2p6 3s2 3p6 4s2
Noble gas notation: [Ar] 4s2
Orbital diagram
↑↓
1s↑↓
2s↑↓↑↓↑↓
2p↑↓
3s↑↓↑↓↑↓
3p↑↓
4s- Valence electrons
- 2
- Unpaired electrons
- 0
- Block
- s-block
- Magnetism (atom)
- diamagnetic
Electrons per shell
| K (n = 1) | 2 |
|---|---|
| L (n = 2) | 8 |
| M (n = 3) | 8 |
| N (n = 4) | 2 |
Calcium ion configurations
| Ion | Electrons | Configuration |
|---|---|---|
| Ca2+ | 18 | [Ne] 3s2 3p6 |
How to write it
Place 20 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. Calcium sits in period 4, group 2, in the s-block, so its last electron enters an s subshell. Replacing the inner electrons with the previous noble gas gives the shorthand [Ar] 4s2.
Try calcium and its ions in the calculator, or see the full calcium data sheet.
Calcium electron configuration FAQ
What is the electron configuration of calcium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s². Shorthand (noble gas) notation: [Ar] 4s².
What is the noble gas configuration of calcium?
[Ar] 4s². The bracket stands for the Ar core electrons.
How many valence electrons does calcium have?
2 (outer shell (n = 4)).
How many unpaired electrons does calcium have?
0 in the ground state, following Hund’s rule. With all electrons paired, the atom is diamagnetic.
What is the electron configuration of Ca2+?
[Ne] 3s² 3p⁶ (18 electrons).