Regular Tetrahedral structure is possible in
sp3 hybridization where central atom has 4 bond pair and no lone pair.
(a)
XeF4 is
sp3d2 hybridised and structure is square planar.
(b)
[Ni(CN)4]−2 is coordinate compound and oxidation number of
Ni is
+2.
Electronic configuration of
Ni+2 is
=[Ar]3d8
But because of
CN−ion which is a strong field ligand, it can perform pairing of electron.
And the structure of
dsp2 hybridization is square planar.
(C)
BF4−,4 bond pair present so angle is
109∘28′ and
sp3 hybridised. So structure is regular tetrahedral.
(d)
SF4 is
sp3d hybridised and structure is see-saw.