explain the structure of PCl5

In PCl_{5} molecule, P forms 5 bonds with 5 Cl atoms, therefore it has to unpair 5 electrons. Now, the electronic configuration of phosphorus can be written as:

P : 1s^{2}2s^{2}2p^{6}3s^{2}3p^{3}.

So P unpairs its, 3s^{2} electron and one of the 3s electron is promoted to the empty 3d orbital.

P : 1s^{2}2s^{2}3s^{1}3p^{3}3d^{1}.

Thus, P atom undergoes sp^{3}d hybridization and forms 5 equivalent sp^{3}d orbitals, each contain an unpaired electron. These hybrid orbitals arrange themselves in a trigonal bipyramidal structure, and each hybrid orbital overlaps with the 2p_{z} orbital of Cl atom containing one electron, leading to formation of 5 P-Cl sigma bonds directed at the coreners of a regular trigonal bipyramidal structure. Thus, geometry of PCl_{5} molecule can be shown as:

**
**