Question

In $PC{l_5}$ , the three $P - Cl$ bonds in the plane are called?

Answer 1

Hint : The elements that are present in the third period of periodic table have $d$ orbitals also along with $s$ and $p$ orbitals. The energy of $3d$ orbitals is close to the energy of $3s$ and $3p$ orbitals. The energy of $3d$ orbitals is also equal to the energy of $4s$ and $4p$ orbitals. So, the hybridization is favorable involving either $3d$ , $3s$ , $3p$ or $3d$ , $4s$ , $4p$ .

Complete Step By Step Answer:
The molecular geometry of $PC{l_5}$ is trigonal bipyramidal. The electron region distribution around the central atom is symmetric. Phosphorus undergoes $s{p^3}d$ hybridization and the geometry will be trigonal bipyramidal. The five valence electrons are shared with one electron each from five chlorine atoms. The structure of $PC{l_5}$ is given below.

All the $P - Cl$ bonds in the $PC{l_5}$ molecule are not the same. Two $P - Cl$ bonds are longer and they are less stable. These bonds are called axial $P - Cl$ bonds. The other three $P - Cl$ bonds are more stable and are called equatorial $P - Cl$ bonds. These are the result of greater bond pair-bond pair repulsion in the axial bonds. Phosphorus pentachloride molecules form five bonds in order to expand the octet configuration and to have more place to insert bonding pairs of electrons. The three bonds in the plane are called planar bonds. These are also called equatorial bonds.
Therefore, the three $P - Cl$ bonds in a plane are called equatorial bonds.

Note :
Phosphorus pentachloride is green-yellowish in color and exists as a solid in nature. It has a structure like that of a salt in the crystalline state. It is used as a chlorinating agent and also as a catalyst in the manufacturing of organic chemicals, dyes, etc. It is used as a chlorinating agent. It is used in the pharmaceutical industry in the manufacture of penicillin and cephalosporin.