In which of the following pairs, both the species are not isostructural?

1. $\mathrm{S}\mathrm{i}\mathrm{C}{\mathrm{l}}_4,\mathrm{ }{\mathrm{P}\mathrm{C}\mathrm{l}}_4^{+}$
2. Diamond, silicon carbide
3. $\mathrm{N}{\mathrm{H}}_3,\mathrm{ }\mathrm{P}{\mathrm{H}}_3$
4. $\mathrm{X}\mathrm{e}{\mathrm{F}}_4,\mathrm{ }\mathrm{X}\mathrm{e}{\mathrm{O}}_4$

Solution

i. Hybridization of $\mathrm{N}{\mathrm{H}}_3\mathrm{ }\left[\mathrm{\sigma }=3,\mathrm{ }\mathrm{l}\mathrm{p}=1\right]$
$\mathrm{s}{\mathrm{p}}^3$ geometry : Tetrahedral

ii. Structures of $\mathrm{X}\mathrm{e}{\mathrm{F}}_4$ is square planar.

Structure of $\mathrm{X}\mathrm{e}{\mathrm{O}}_4$ is tetrahedral

So $\mathrm{X}\mathrm{e}{\mathrm{F}}_4$ and $\mathrm{X}\mathrm{e}{\mathrm{O}}_4$ are not isostructural.
iii. Structure of $\mathrm{S}\mathrm{i}\mathrm{C}{\mathrm{l}}_4$ is tetrahedral.

Structure of ${\mathrm{P}\mathrm{C}\mathrm{l}}_4^{+}$ is tetrahedral.

iv. Diamond and SiC both are isostructural because both have tetrahedral arrangement and central atom is $\mathrm{s}{\mathrm{p}}^3$ hybridized.

Asked in: NEET 2015 (Phase 2)

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