Question

(i) Why are interhalogen compounds more reactive than halogens ?
(ii) All the five bonds in $PC{l}_5$ are not equivalent. Justify.

Answer 1

(i) Interhalogen compounds are more reactive than all halogens except $F$. The interhalogen bonds (A-X) are weaker than the bonds between halogen atoms (X-X) in dihalogen compounds. The main reason for this is that the electronegativities of atoms in a diahalogen compound are the same while that of atoms in interhalogen compounds are different. Thus, the bond in interhalogen compounds is polarised, because of which it can break more easily. For example, the bond between $ICl$ is weaker than $I_2$ because $ICl$ atom is more polarised due to a difference in electronegativities of the two atoms.

(ii) The five bonds in $PC{l}_5$ are not equivalent. $PC{l}_5$ is $s{p}^{3}d$ hybridised. Two chlorine atoms are located axially at the top and bottom of the molecule while the remaining three are attached equatorially. The length of the axial and equatorial bonds between $P$ and $Cl$ is different.