Question

The exhibition of highest co – ordination number depends on the availability of vacant orbitals in the central atom. Which of the following elements is not likely to act as central atom in $MF_{6}^{3 -}$?

• A. B
• B. Al
• C. Ga
• D. In

Answer 1

Answer: (A)

B

Answer 2

: Due to non – availability of d- orbitals, boron is restricted to a maximum covalence of four (using) 2s and three 2p orbitals) while others (Al, Ga, In) can expand their covalence above four by using their 3d orbitals. Thus, B forms only $\lbrack BF_{4}\rbrack^{-}$ and others form $\lbrack MF_{6}\rbrack^{3 -}$