Question

What is the shape and hybridization of the ${\mathrm{PCl}}_3$ molecule?

Answer 1

Hybridization:

• It is the process of intermixing of the orbitals of slightly different energies so as to redistribute their energies, resulting in the formation of a new set of orbitals of equivalent energies and shapes.
• The hybridized orbitals are always equivalent in energy and shape.

Formula used to calculate the hybridization of a molecule

• $\mathrm{Number}\mathrm{of}\mathrm{electron}\mathrm{pair}=\frac{1}{2}[\mathrm{V}+\mathrm{N}-\mathrm{C}+\mathrm{A}]$

where,

$\mathrm{V}$ is the number of valence electrons present in the central atom

$\mathrm{N}$ is the number of monovalent atoms bonded to the central atom

$\mathrm{C}$ is the charge of cation

$\mathrm{A}$ is the charge of anion

• The given molecule is, ${\mathrm{PCl}}_3$

$\mathrm{Number}\mathrm{of}\mathrm{electron}\mathrm{pair}=\frac{1}{2}\times [5+3-0+0]=\frac{8}{2}=4$

The number of electron pairs is $4$ which means the hybridization will be ${\mathrm{sp}}^3$ and the electronic geometry of the molecule will be tetrahedral.

But as there are $3$ atoms around the central phosphorous atom, the $4^{\mathrm{th}}$ position will be occupied by lone pair of electrons. Hence the molecular geometry will be trigonal pyramidal.

Therefore, the shape and hybridization of the ${\mathrm{PCl}}_3$ molecule are trigonal pyramidal and ${\mathrm{sp}}^3$ respectively.