Which one of the following elements is unable to form M F 6 3 - ion?

Question

Which one of the following elements is unable to form M F 6 3 - ion?, B, Al, Ga, In

MARKS App · Accepted Answer

As ‘B’ has no d-orbitals, so it can’t extend its covalency beyond 4. Hence, ‘B’ cannot form the ion like

{MF}_{6}^{3 -}

, i.e.,

{BF}_{6}^{3 -}

.
As all other metals have vacant d-orbitals in their valence shells, so they can extend their covalency beyond 4.