When two different halogens react with each other, interhalogen compounds are formed. They can be assigned general compositions as XX’ , XX’_3, XX’₅ and XX’₇ where X is halogen of larger size and X’ of smaller size and X is more electropositive than X’. As the ratio between radii of X and X’ increases, the number of atoms per molecule also increases. Thus, iodine (VII) fluoride should have maximum number of atoms as the ratio of radii between I and F should be maximum. That is why its formula is IF₇ (having maximum number of atoms).

What are interhalogen compounds used as?

Non-aqueous solvents

If we come to the uses of the interhalogen compounds, then one of its main uses is to act as the halogenating agent, i.e., they are used to form other halogen compounds like BrF₅. Interhalogen compounds of fluorine are very useful fluorinating agents.