Question

How many of the following interhalogen species have 2 lone pairs of electrons on the central atom?
$Cl{F}_3,Cl{F}_2^{-},Cl{F}_5$ and $IC{l}_2^{+}$

Answer 1

We know,
$\text{Number of lone pairs}=\frac{\text{Total number of electrons available - Number of bonded electrons}}{2}$

In $Cl{F}_3$, the total number of electrons around the central atom $=7+3=10$
$\text{Number of lone pairs on the central atom}=\frac{10-6}{2}=\frac{4}{2}=2$

In $Cl{F}_2^{-}$, the total number of electrons around the central atom $=7+2+1=10$
$\text{Number of lone pairs on the central atom}=\frac{10-4}{2}=\frac{6}{2}=3$

In $Cl{F}_5$, the total number of electrons around the central atom $=7+5=12$
$\text{Number of lone pairs on the central atom}=\frac{12-10}{2}=\frac{2}{2}=1$

In $IC{l}_2^{+}$, the total number of electrons around the central atom $=7+2-1=8$
$\text{Number of lone pairs on the central atom}=\frac{8-4}{2}=\frac{4}{2}=2$

$\therefore Cl{F}_3$ and $IC{l}_2^{+}$ have 2 lone pairs of electrons on the central atom.