Halogen

Chlorine

Chlorine (Cl) has atomic number 17. PubChem classifies it as halogen.

Atomic number

17

Symbol

Cl

Atomic weight (source value)

35.45

Electron configuration

[Ne]3s2 3p5

Standard state

Gas

Electronegativity (Pauling)

3.16

Melting point (K)

171.65

Boiling point (K)

239.11

Density (g/cm³)

0.003214

Oxidation states

+7, +5, +1, -1

Understanding this entry

Atomic number is the number of protons in the nucleus. Properties are reference values and may depend on conditions and measurement conventions. An atomic weight is not the mass of every isotope. For elements without a standard atomic weight, a source may report an isotope mass number. Blank source values are shown as unavailable rather than estimated.

Further reading and reference: NIH PubChem source dataset ↗. Values and educational summaries are not a substitute for specialised advice.