Periodex

General properties

Group

group 17 (halogens)

Period

period 3

Category

halogens

Standard atomic weight

35.45

[35.446, 35.457]

Melting point

(Cl₂) 171.6 K (-101.5 °C)

Boiling point

(Cl₂) 239.11 K (-34.04 °C)

Phase at STP

gas

Additional properties

Block

p-block

Electron configuration

[Ne] 3s² 3p⁵

Electrons per shell

2, 8, 7

Electronegativity

3.16

Density

3.2 g/L

Oxidation states

−1, +1, +2, +3, +4, +5, +6, +7 (a strongly oxide)

CAS Number

7782-50-5

Natural isotopes

Discovery history

Discovered by

Carl Wilhelm Scheele

Year of discovery

1774

Origin of name

The Greek 'chloros', meaning greenish yellow