Interhalogen compounds are formed either by direct combination between the halogens or by the action of a halogen on a lower interhalogen.
e.g., Cl2(g)+F2(g)Equal Volumes473 K−−−→2CIF(g)
CIF(g)+F2(g)475−575K−−−−−−→CIF3(g)
Their general composition can be assigned as XX′n, where X is a less electronegative halogen while X' is a more electronegative halogen and n is the number of such atoms. Depending upon oxidation state of X, these are of four types:
(a) XX′(e.g.,CIF) (b) XX′3(e.g.,CIF3)
(c) XX′5(e.g.,BrF5) (d) XX′7(e.g.,IF7)