Question

Explain the following:
i) Why are interhalogen compounds more reactive than halogens?
ii) All the five bonds in $PC{l_5}$ are not equivalent. Justify.

Answer 1

Hint- Electronegativities of atoms in a halogen compound are the same while that of atoms in interhalogen compounds are different. So, the bond in interhalogen compounds is polarised, because of which it can break more easily and $PC{l_5}$ is $s{p^3}d$ hybridised. Use these two concepts to reach the answer.

Complete answer:
i) Interhalogen compounds are generally highly reactive and are more reactive compared to all the halogens except \[F\] . The interhalogen bonds $\left( {A - X} \right)$ are mostly weak as compared to the bonds between the two halogen atoms $\left( {X - X} \right)$ in any dihalogen compounds. The key explanation for this is that atoms in a halogen compound have the same electronegativity while atoms in interhalogen compounds are different. The bond in interhalogen compounds is therefore polarised, which makes it easier to break. 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 as it 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.

Note- Electronegativity is a measure of an atom's ability to attract shared electrons to itself. Electronegativity generally increases on the periodic table as you move over a period from left to right, and decreases as you move down a group. The electronegativity of an element helps us to determine how much electrons it wishes to gain or lose in a chemical reaction and its compound is ionic, polar or nonpolar due to the difference in electronegativity