Question

Electron deficient molecule is

• A. $CC{l}_4$
• B. $PC{l}_5$
• C. $B{F}_3$
• D. $S{F}_6$

Answer 1

Answer: (C)

The compounds in which central atom has less than $8$ electrons in their valence shell are electron deficient compounds.
(a) $CC{l}_{4}Cl-\underset{\stackrel{|}{C}l}{\stackrel{\underset{|}{C}l}{C}}-Cl$
Carbon (central atom) has $8$ electrons in valence shell, $4$ from carbon and $1$ electron each from four chlorine atom.

Phosphorus (central atom) has $10$ electrons in valence shell, $5$ from $P$ and one each from five chlorine atoms.

Boron (central atom) has $6$ electrons in valence shell, $3$ from boron and one each from three fluorine atoms.
$\because$ Boron in $B{F}_3$ has less than $8$ electrons.
$\therefore$ it is electron deficient molecule and is correct answer.

Sulphur (central atom) has $12$ electrons in valence shell, $6$ from sulphur and one each from six fluorine atoms.