Isostructural species are those which have the same shape and hybridisation. Among the given species identify the isostructural pairs. (i) [NF3 and BF3] (ii) [BF4- and NH4+] (iii) [BCl3 and BrCl3] (iv) [NH3 and NO3-]
Isostructural species are those which have the same shape and hybridisation. Among the given species identify the isostructural pairs. (i) [NF3 and BF3] (ii) [BF4- and NH4+] (iii) [BCl3 and BrCl3] (iv) [NH3 and NO3-]

From a structural standpoint, we can see that,

NF3

is pyramidal whereas

BF3 

is planar triangular.

BF4

and

NH4+

ions are tetrahedral in structure.

BCl3

is triangular planar and 

BrCl3

is pyramidal.

NO3

is triangular planar and 

NH3

is pyramidal.

Only option B has both molecules of similar structure.