Chlorine (Cl)

Greenish-yellow gas

Chlorine is a greenish-yellow gas used to disinfect drinking water and swimming pools, and as a halogen with [Ne] 3s² 3p⁵ configuration, chlorine has a high electron affinity (3.61 eV) and readily gains one electron to form Cl⁻. It was the first chemical weapon used in World War I.

Key metrics

Density0.003214g/cm³

Melting point171.6K

Boiling point239.11K

Electronegativity3.16Pauling

Discovery

1774discovered

Discovered by: Carl Wilhelm Scheele
Reactivity profile: Strong Oxidizer
Reactivity: High
Bonding: Covalent

Electron configuration

\textcolor{#6b7280}{[Ne]}\; \textcolor{#ef4444}{3_{s}^{2}}\; \textcolor{#3b82f6}{3_{p}^{5}}

[Ne] 3s2 3p5

Wave function

\Psi_{\text{Cl}} \approx \frac{1}{\sqrt{17!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{17}(\mathbf{r}_{17}) \right|

Probability density $|\Psi|^2$ across the Cl valence shell.

Crystal structure

Orthorhombic

Lattice constantsa 1.00 · b 1.30 · c 0.90

Cell anglesα = β = γ = 90°

Coordination number—

Atoms per cell—

Atomic packing factor0.60

Physical properties

Atomic radius: 99 pm
Ionization energy: 1251 kJ/mol
Electron affinity: 349 kJ/mol
Crystal structure: Orthorhombic

Oxidation states

-1+1+3+5+7

Acid/base

Acidic

Strongly acidicStrongly basic

State at 25 °CGas

171.6 K239.11 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

500.8nmCl ICyan60%

542.4nmCl I (green)Green100%

613.3nmCl IOrange40%

Dominant line 542.4 nmRange 501–613 nmTransitions 3