This table summarises some of the properties and uses of three halogens:
|Element||Appearance (room temperature)||Properties||Typical use|
|Chlorine||Yellow-green gas||Toxic – kills bacteria||Sterilising water|
|Bromine||Red-brown liquid||Toxic – kills bacteria||[Not required]|
|Iodine||Grey solid||Toxic – kills bacteria||Antiseptic 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).