Question

What is an interhalogen compound? Describe the geometry of $A{B}_3{E}_2$ type chlorine-fluorine interhalogen compounds.

Answer 1

The reaction of halogens with themselves gives a number of compounds called interhalogen compounds. They are of the form $XY,X{Y}_3,X{Y}_5,X{Y}_7$ where $X$ is a larger size halogen and $Y$ is smaller size halogen.

Examples: $Br{F}_3$, $Br{F}_5$, $I{F}_7$.

Geometry of $Cl{F}_3$: The $A{B}_3{E}_2$ geometry gives the trigonal bipyramidal arrangement of valence electrons around $Cl$. There are three possible arrangement of lone pairs $A,B$ and $C$. Out of these, the one with minimum repulsion is favourable. As per VSEPR theory, the order of repulsion force is lone-pair-lone pair > lone pair-bond pair>bond pair-bond pair.

Structure $A:$ 6 lone pair-bond pair repulsions

$B:$ 4 lone pair-bond pair repulsions

$C:$ 1 lone pair-lone pair and 2 lone pair-bond pair repulsions

Therefore, structure $B$ with least repulsion forces is the stable structure and is called T-shape.