Among the following the pair in which the two species are not isostructural is:

Among the following the pair in which the two species are not isostructural is:
  1. $\mathrm{SiF}_4$ and $\mathrm{SF}_4$
  2. $\mathrm{IO}_3^{-}$and $\mathrm{XeO}_3$
  3. $\mathrm{BH}_4^{-}$and $\mathrm{NH}_4^{+}$
  4. $\mathrm{PF}_6^{-}$and $\mathrm{SF}_6$

Solution

$\mathrm{SiF}_4$ and $\mathrm{SF}_4$ are not isostructural because $\mathrm{SiF}_4$ is tetrahedral due to $s p^3$ hybridisation while $\mathrm{SF}_4$ has distorted tetrahedral geometry due to presence of lone pair.

Related Theory Two molecules are isostructural if they have a similar number of atoms arranged in a similar structure (spatial coordinates). Caution If they have same number of lone pair and bond pair, they are considered as isostructural.

Asked in: NEET 2004

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