Properties and uses of the halogens

This table summarises some of the properties and uses of three halogens:

ElementAppearance (room temperature)PropertiesTypical use
ChlorineYellow-green gasToxic – kills bacteriaSterilising water
BromineRed-brown liquidToxic – kills bacteria[Not required]
IodineGrey solidToxic – kills bacteriaAntiseptic used during hospital procedures

Iodine forms a purple vapour when it is warmed.

All of the halogens exist as diatomic molecules. This means that the elements are made up of pairs of atoms that are chemically joined together (for example, fluorine exists as F2, chlorine as Cl2, bromine as Br2 and iodine as I2).