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FOCUS POINT --- P Block elements -- Episode 5

INTER HALOGEN COMPOUNDS

When two different halogens react with each other, interhalogencompounds 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 electronegative 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 IF 7 (having maximum number of atoms). Preparation The inter halogen compounds can be prepared by the direct Combination or by the action of halogen on lower inter halogen compounds. The product formed depends upon some specific conditions, For example, Examples ClF , ClF3 , BrF5 , IF7

SStructure

Their molecular structures are very interesting which can be explained on the basis of VSEPR theory The XX3 compounds have the bent ‘T’shape, XX 5 compounds square pyramidal and IF7 has pentagonal bipyramidal structures Magical chemistry ,HSS Chemistry Tutorials Website www.ftachemmagic.com you tube channel www.youtube.com/c/ftavlog

properties 1.They are volatile solids or liquids 2.These are all covalent molecules 3.Their m.p. and b.p. are a little higher than individual halogen atoms 4.diamagnetic in nature. 5. In general, inter halogen compounds are more reactive than halogens (except fluorine). This is because X–X′ bond in Inter halogens is weaker than X–X bond in halogens except F–F bond. 6. All these undergo hydrolysis giving a. halide ion derived from the smaller halogen and a b. hypohalite ( when XX′), c. halite ( when XX′ 3 ), d. halate (when XX′ 5 ) and e. perhalate (when XX′ 7 ) anion derived from the larger halogen. XX ' + H 2 O → HX ' + HOX 1. Discuss the molecular shape of BrF 33 onon thethe basisbasis ofof VSEPRVSEPR theory.?theory.? Solution The central atom Br has seven electrons in the valence shell. Three of these will form electron- pair bonds with three fluorine atoms leaving behind four electrons. Thus, there are three bond pairs and two lone pairs. According to VSEPR theory, these will occupy the corners of a trigonal bipyramid. The two lone pairs will occupy the equatorial positions to minimise lone pair-lone pair and the bond pair-lone pair repulsions which are greater than the bond pair-bond pair repulsions. In addition, the axial Magical chemistry ,HSS Chemistry Tutorials Website www.ftachemmagic.com you tube channel www.youtube.com/c/ftavlog fluorine atoms will be bent towards the equatorial fluorine in order to minimise the lone-pair-lone pair repulsions. The shape would be that of a slightly bent ‘T’. Uses 1. These compounds can be used as non aqueous solvents. 2. Interhalogen compounds are very useful fluorinating agents.

Intext Question

1.Why is ICl more reactive than I 2 ? This is because I–Cl′ bond in Inter halogens is weaker than X–X bond in halogens except I–I bond.

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