17
Cl
Chlorine
35.45
Chlorine (Cl)
HalogenGroup 17Period 3p-block-block
Chlorine is a chemical element with symbol Cl and atomic number 17. It also has a relative atomic mass of 35.5. Chlorine is in the halogen group (17) and is the second lightest halogen following fluorine.
Latin name: Chlorum
Atomic Number
17
Atomic Mass
35.45 g/mol
Phase (STP)
Gas
Electron Config.
[Ne] 3s² 3p⁵
General
SymbolCl
Atomic Number17
Atomic Mass35.45 g/mol
CategoryHalogen
Group17
Period3
Blockp-block
Electron Configuration[Ne] 3s² 3p⁵
Valence Electrons7
ColourPale yellow-green gas
Appearancepale yellow-green gas
CAS NumberCAS7782-50-5
Physical Properties
Phase (STP)Gas
Density0.003214 g/cm³
Melting Point-101.50°C · -150.70°F · 171.65 K
Boiling Point-34.04°C · -29.27°F · 239.11 K
Atomic Properties
Atomic Radius79 pm
Covalent Radius102 pm
Van der Waals Radius175 pm
Electronegativity3.16 Pauling
Ionization Energy1251 kJ/mol
Electron Affinity349 kJ/mol
Oxidation States-1, +1, +2, +3, +4, +5, +6, +7
Ion ChargeCl⁻
Electromagnetic
Electrical TypeInsulator
Abundance
In Universe0.00009999999999999999%
In Sun0.00007999999999999999%
In Earth's Crust1.7000%
In Oceans1.9000%
In Humans0.1200%
In Meteorites0.3700%
Discovery & History
Discovery Year1774
Discovered ByCarl Wilhelm Scheele
Isotopes of Chlorine
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Cl-35 | 75.76% | Stable | — |
| Cl-36 | — | 3.01 × 10⁵ years | β⁻, EC |
| Cl-37 | 24.24% | Stable | — |