Which one of following elements is unable to from `MF_(6)^(3-)` ion?

Options

A. B
B. Al
C. Ga
D. In

Answer

A

Explanation

Boron belongs to 2nd period of the periodic table with electronic configuration `1s^(2), 2s^(2),2p^(1)`. It does not have vacant d-orbitals, thus cannot increase its covalency above four.
Therefore, boron (B) cannot form `MF_(6)^(3-)` ion. In contrast, aluminium (Al), gallium (Ga), indium (In) have the vacant 3d-orbitals, thus can increase their covalence above four and form `MF_(6)^(3-)` ion.