Interhalogen Compounds - Practice Questions & MCQ

When two different halogens react with each other, interhalogen compounds are formed. They can be assigned general compositions as XX′, XX₃′, XX₅′ and XX₇′ 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).

Preparation
The interhalogen compounds can be prepared by the direct combination or by the action of halogen on lower interhalogen compounds. The product formed depends upon some specific conditions, For example,

Properties
Some properties of interhalogen compounds are given in the following table.

These are all covalent molecules and are diamagnetic in nature. They are volatile solids or liquids at 298 K except ClF which is a gas. Their physical properties are intermediate between those of constituent halogens except that their m.p. and b.p. are a little higher than expected.
Their chemical reactions can be compared with the individual halogens. In general, interhalogen compounds are more reactive than halogens (except fluorine). This is because X–X′ bond in interhalogens is weaker than X–X bond in halogens except F–F bond. All these undergo hydrolysis giving halide ion derived from the smaller halogen and a hypohalite ( when XX′), halite (when XX′₃), halate (when XX′₅) and perhalate (when XX′₇) anion derived from the larger halogen.

Their molecular structures are very interesting which can be explained on the basis of VSEPR theory. The XX₃ compounds have the bent ‘T’ shape, XX₅ compounds square pyramidal and IF₇ has pentagonal bipyramidal structures.