JEE Main · 2012 · 29 Apr 2012 · Offline · Chemical Bonding and Molecular Structure

Isostructural species share the same shape and hybridisation. Carbonate and nitrate are both trigonal planar and $\mathrm{s}{\mathrm{p}}^2$; $\mathrm{PC}{\mathrm{l}}_4^{+}$ and $\mathrm{SiC}{\mathrm{l}}_4$ are both tetrahedral and $\mathrm{s}{\mathrm{p}}^3$; $\mathrm{Al}{\mathrm{F}}_6^{3-}$ and $\mathrm{S}{\mathrm{F}}_6$ are both octahedral and $\mathrm{s}{\mathrm{p}}^3{\mathrm{d}}^2$. But $\mathrm{P}{\mathrm{F}}_5$ is trigonal bipyramidal $\mathrm{s}{\mathrm{p}}^3\mathrm{d}$ with no lone pair, whereas $\mathrm{Br}{\mathrm{F}}_5$ is square pyramidal $\mathrm{s}{\mathrm{p}}^3{\mathrm{d}}^2$ with one lone pair, so that pair is not isostructural.