Chlorine (Cl)
[Ne] 3s² 3p⁵. 1 unpaired electron, period 3, group 17, p 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.
ClChlorine, Z = 17, 35.45 u
[Ne] 3s2 3p5
In full: 1s² 2s² 2p⁶ 3s² 3p⁵
- Blockp block
- Period3
- Group17
- Valence7
- Unpaired1
- MagneticPara
Last electron 3p
- n3shell
- l1p subshell
- m0orbital
- s−½spin down
Step by step
- Chlorine has 17 electrons.
- Fill in (n + l) order: 1s² 2s² 2p⁶ 3s² 3p⁵.
- Write the subshells in order of n: 1s² 2s² 2p⁶ 3s² 3p⁵.
- Replace the neon core with [Ne]: [Ne] 3s² 3p⁵.
Chlorine (Cl): the numbers
| Atomic number | 17 |
|---|---|
| Atomic mass | 35.45 u |
| Period | 3 |
| Group | 17 |
| Block | p block |
| Valence electrons | 7 |
| Unpaired electrons | 1 |
| Magnetic | paramagnetic |
| Last electron | 3p: n = 3, l = 1, m = 0, s = −1/2 |
Chlorine (Cl): quick answers
What is the electronic configuration of chlorine?
Chlorine has 17 electrons: 1s² 2s² 2p⁶ 3s² 3p⁵, or [Ne] 3s² 3p⁵ in short.
How many unpaired electrons does chlorine have?
Chlorine has 1 unpaired electron, so it is paramagnetic. Put one electron in each box of a subshell before pairing (Hund’s rule) to see them.
What are the quantum numbers of the last electron of chlorine?
The last electron goes into 3p: n = 3, l = 1, m = 0, s = −1/2. Orbitals fill from m = −l up, spin +½ first.