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Correct Option : B
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Amongst hexahalides of sulphur, only SF6 is exceptionally stable for steric reason.
In SCl6, smaller S cannot accomodate six larger Cl– ions.
PH5 does not exist as there is large difference in the energies of s, p and d orbitals of P and hence it does not undergo sp3d hybridisation.
NCl5 does not exist as there is no d-orbital with N.
BF6 3– does not exist as there is no vacant d-orbital in B and hence it cannot exceed its covalency beyond four.