Question

Explain why $PC{l}_5$ trigonal bipyramidal whereas $I{F}_5$ is square pyramidal.

Answer 1

Shape of $PC{l}_5$ molecule

* In $PC{l}_5$ the central atom is surrounded by five bond pairs and no lone paris.

* Hybridisation of central atom in $PC{l}_5$ molecule is $s{p}^{3}d$ giving trigonal bipyramidal shape.


Shape of $I{F}_5$ molecule

* In $I{F}_5$ molecule central atom is surrounded by five bond pairs and one lone pair.

* Hybridisation of central atom in $I{F}_5$ molecule is $s{p}^3{d}^2$ giving square pyramidal shape.



So, shape of $PC{l}_5$ is different from $I{F}_5$ because central atom in $I{F}_5$ molecule have one extra lone pair.