Chlorine (Cl)

Chlorine is a chemical element with symbol Cl and atomic number 17. It is the second-lightest of the halogens. Its properties are mostly intermediate between those of its periodic table neighbors fluorine and bromine.

Atomic Number

17

Atomic Mass

35.45 u

Category

halogen

Phase

gas

Density

0.003214 g/cm³

Electron Shells

2, 8, 7

Atomic Structure

Protons: 17 • Electrons: 17 • Neutrons: Varies by isotope

Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁵

Discovery

1774 • Carl Wilhelm Scheele