In which of the following pairs , the two species are not isostructural ? `PCl_4^(+)` and `SiCl_4`, `PF_5` and `BrF_5`, `AlF_6^(3-)` and `SF_6`, `CO_3^(2-)` and `NO_3^(-)`

Options

A. ` PCI_(4)^(+) and SiCl_(4)`
B. `PF_5 and BrF_5`
C. `AIF_(6)^(3-) and SF_6`
D. `CO_(3)^(2-) and NO_(3)^(-)`

Answer

B

Explanation

`PF_5 (sp^3d)` has trigonal bipyramidal geometry while `BrF_5 (sp^3d^2)` has square pyramidal or distorted octahedral geometry. All the remaining have the same structure: `PCI_(4)^(+) SiCl_4 `, (tetrahedral, `sp^(3-) , AIF_(6)^(3-)` - and `SF_6`) (octahedral, `sp^3 d^2`) and `CO_(3)^(2-)` and `NO_(3)^(-)` (trigonal planar, `sp^2`).