Question

Consider the following molecules/ions:
(1) $S{F}_4$ (2) $C{F}_4$ (3) $Xe{F}_4$ (4) ${B{F}_4}^{-}$
Which pair doesnot contain lone pair of electrons around its central atom?

• A. $1$ and $2$
• B. $2$ and $4$
• C. $2$ and $3$
• D. $1$ and $4$

Answer 1

Answer: (B)

$2$ and $4$

(1) In $S{F}_4$, the central $S$ atom has $6$ valence electrons, out of which $4$ are involved in the formation of $4S-F$ bonds. The remaining $2$ electrons are present as a lone pair.
(2) In $C{F}_4$, the carbon atom has $4$ valence electrons, all of which are involved in the formation of bonds with four $F$ atoms. Hence, no lone pairs are present.

(3) In $Xe{F}_4$, the $Xe$ atom has $8$ valence electrons out of which $4$ are involved in the formation of bonds with four $F$ atoms. Hence, two lone pairs are present.
(4) In $B{F}_4^{-}$, the $B$ atom has $4$ valence electrons all of which are involved in the formation of bonds with four $F$ atoms. Hence, no lone pairs are present.