Copper (Cu)
[Ar] 3d¹⁰ 4s¹, an exception. 1 unpaired electron, period 4, group 11, d block.
Element or ion
Type a symbol, a name or an atomic number, add a charge such as Fe3+ or Cl-, or tap an element in the table. Orbitals fill from m = −l up, spin +½ first.
CuCopper, Z = 29, 63.546 u
[Ar] 3d10 4s1
In full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹
- Blockd block
- Period4
- Group11
- Valence11
- Unpaired1
- MagneticPara
Last electron 3d
- n3shell
- l2d subshell
- m+2orbital
- s−½spin down
Why Cu is an exception
Plain filling would give [Ar] 3d⁹ 4s². A completely filled d subshell (d¹⁰) is extra stable, for the same reasons of symmetry and exchange energy. So one s electron moves into d.
Step by step
- Copper has 29 electrons.
- Fill in (n + l) order: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁹.
- That gives [Ar] 3d⁹ 4s², but the accepted configuration is [Ar] 3d¹⁰ 4s¹. A completely filled d subshell (d¹⁰) is extra stable, for the same reasons of symmetry and exchange energy. So one s electron moves into d.
- Write the subshells in order of n: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹.
- Replace the argon core with [Ar]: [Ar] 3d¹⁰ 4s¹.
Copper (Cu): the numbers
| Atomic number | 29 |
|---|---|
| Atomic mass | 63.546 u |
| Period | 4 |
| Group | 11 |
| Block | d block |
| Valence electrons | 11 |
| Unpaired electrons | 1 |
| Magnetic | paramagnetic |
| Last electron | 3d: n = 3, l = 2, m = +2, s = −1/2 |
Copper (Cu): quick answers
What is the electronic configuration of copper?
Copper has 29 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹, or [Ar] 3d¹⁰ 4s¹ in short.
Why is copper [Ar] 3d¹⁰ 4s¹ and not [Ar] 3d⁹ 4s²?
A completely filled d subshell (d¹⁰) is extra stable, for the same reasons of symmetry and exchange energy. So one s electron moves into d.
What are the quantum numbers of the last electron of copper?
The last electron goes into 3d: n = 3, l = 2, m = +2, s = −1/2. Orbitals fill from m = −l up, spin +½ first.