Question

Which of the following pairs are isostructural?

• A. $Xe{F}_2,I{F}_2^{-}$
• B. $N{H}_3,B{F}_3$
• C. $C{O}_3^{-2},S{O}_3^{-2}$
• D. $PC{l}_5,IC{l}_5$

Answer 1

The correct option is A $Xe{F}_2,I{F}_2^{-}$

Hybridization can be calculated by finding out the steric number for any molecule. The molecules having the same hybridisation have the same geometry.

Option (a)
Steric number of $Xe{F}_2$ = 2 + 3 = 5
(2 bond pairs and 3 lone pairs)
Steric number of $I{F}_2^{-}$ = 2 + 3 = 5
(2 bond pairs and 3 lone pairs)

In $Xe{F}_2,Xe$ is $s{p}^{3}d$ hybridized and linear in shape due to the presence of three lone pairs on the $Xe$ atom (lone pairs occupy the equatorial positions).
In $I{F}_2^{-}$, $I$ atom is also $s{p}^{3}d$ hybridized and is linear in shape due to the presence of three lone pairs on the $I$ atom.

Option (b) The steric numbers of nitrogen and boron in $N{H}_3$ and $B{F}_3$ are 4 and 3 respectively. So, different structures are observed.

Option (c) The steric numbers of carbon and sulfur in $C{O}_3^{2-}$ and $S{O}_3^{2-}$ are 3 and 4 respectively. So, different structures are observed.

Option (d) The steric numbers of phosphorous and iodine in $PC{l}_5$ and $IC{l}_5$ are 5 and 6 respectively. So, different structures are observed.