About

Chlorine is a pale green, highly reactive gas with a sharp, pungent odor. It is a powerful oxidizing agent widely used for sanitation and disinfection, particularly in swimming pools and for purifying drinking water. It is also a key component of PVC plastic, many solvents, and forms the chloride ion in common table salt (NaCl), which is essential for life.

Atomic Properties

Atomic Number17

Atomic Weight35.45 u

Neutrons (common)18

Electron Configuration[Ne] 3s² 3p⁵

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁵

Electrons per Shell2, 8, 7

Electronegativity3.16

Electron Affinity349 kJ/mol

Oxidation States+7, +5, +3, +1, 0, -1

Covalent Radius99 pm

Van der Waals Radius175 pm

Ionic Radius181 pm

Periodic Table Position

Group17

Period3

BlockP

Chemical SeriesHalogens

Physical Properties

State at STPgas

Appearancepale yellow-green gas

Crystal Structureorthorhombic

Magnetic Orderingdiamagnetic

Speed of Sound206 m/s

Thermal Properties

Melting Point171.6 K

Boiling Point239.11 K

Triple Point172.17 K

Thermal Conductivity0.009 W/(m·K)

Specific Heat0.479 J/(g·K)

Molar Heat33.949 J/(mol·K)

Heat of Fusion6.406 kJ/mol

Heat of Vaporization20.41 kJ/mol

Abundance

In Earth's Crust145 ppm

In Ocean19,400 ppm

In Solar System8.5 ppm

In Human Body1,400 ppm

In Universe1 ppm

Discovery

Discovered byCarl Wilhelm Scheele

Discovery Year1,774

Occurrenceprimordial

CAS Number7782-50-5

Electron Configuration

Energy

↿⇂

↿

Isotopes of Chlorine

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
³⁵Cl	34.968852	75.78%	Stable	Stable
³⁶Cl	35.968306	Trace	301.3 ky	Beta Minus Decay, Electron Capture
³⁷Cl	36.965902	24.22%	Stable	Stable

Interactive Visualization

Explore the 3D Bohr model of Chlorine in our interactive viewer.

View 3D Model of Chlorine