Chlorine

Atomic number

17

Atomic mass (u)

35.45

Category

Halogen

Standard state

Gas

Melting point

-101.5 °C (171.65 K)

Boiling point

-34.04 °C (239.11 K)

Density (g/cm³)

0.003214

Electronegativity (Pauling)

3.16

Electron configuration

[Ne]3s2 3p5

Oxidation states

+7, +5, +1, -1

Atomic radius (pm)

175

First ionization energy (eV)

12.968

Discovery & recognition

Discovery year / period (PubChem)

1774

Discovery credited to (RSC)

Carl Wilhelm Scheele

Date or period recorded by RSC

1774

Discovery place

Not supplied in the structured record; see the RSC history source.

An ancient date does not identify a first human discovery. Different references may date observation, isolation and formal recognition differently.

Natural occurrence & production

The creation of an element’s nuclei and its concentration into terrestrial deposits are different processes. The occurrence note below concerns its presence or production on Earth; it is not a complete account of nucleosynthesis.

“Chlorine is not found uncombined in nature.”

Royal Society of Chemistry · occurrence excerpt ↗

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Reference values are not product specifications. Blank values have not been estimated. For superheavy elements, some properties and family assignments are theoretical or incompletely measured.