Among the following the pair in which the two species are not isostuctural is

Options

A. `SiF_4` and `SF_4`
B. `IO_3^(-)` and `XeO_3`
C. `BH_4^(-)` and `BH_4^(+)`
D. `PF_6^(-)` and `SF_6`

Answer

A

Explanation

Isostructural here means identical shape and geometry. In `SiF_4`, the steric number of `Si` is `4` (four F atoms bonded + zero lone pair). Thus, `SiF_4` has tetrahedral shape and tetrahedral geometry.
In `SF_4`, the steric number of `S` is `5` (four F atoms bonded + one lone pair). Thus, `SF_4` has trigonal bipyramidal geometry but seesaw shape.