Assertion (A)   :The geometry of ${\text{PCl}}_5$ is trigonal bipyramidal.

Reason (R): In  ${\text{PCl}}_5$ three P - Cl bonds lie in one plane make an angle of  $120°$ with each other. The remaining two  P-Cl bonds lying above and below the equatorial plane make an angle of  $90°$  with the   plane.

In ${\text{PCl}}_5$ , the central atom is phosphorus (P).  The electronic configuration of phosphorus is ${\text{1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{\text{2}}{\text{3p}}_{\text{x}}^{\text{1}}3{\text{p}}_{\text{y}}^{\text{1}}3{\text{p}}_{\text{z}}^{\text{1}}$ .  In the first excited state, phosphorus electronic configuration is ${\text{1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{\text{1}}{\text{3p}}_{\text{x}}^{\text{1}}3{\text{p}}_{\text{y}}^{\text{1}}3{\text{p}}_{\text{z}}^{\text{1}}{\text{3d}}^{\text{1}}$ .

In ${\text{PCl}}_5$ ,the five ${\text{sp}}^{\text{3}}\text{d}$  orbitals of phosphorus overlap with the singly occupied p orbitals of chlorine atoms to form five P-Cl sigma bonds. Three P-Cl bonds lie in one plane make an angle of $120°$  with each other.These bonds are termed as equatorial bonds.  The remaining two P-Cl bonds one lying above and other lying below the equatorial plane make an angle of  $90°$  with the plane. These bonds are called axial bonds.  This type of bonding gives trigonal bipyramidal geometry for${\text{PCl}}_5$ .

The structure of ${\text{PCl}}_5$  is as shown below.