EXPLAIN SP ³ D HYBRIDITION WITH AN EXAMPLE .

Sp³d hybridization: In sp³d hybridization, one 's', three 'p' and one 'd' orbitals of almost equal energy intermix to give five identical and degenerate hybrid orbitals, which are arranged in trigonal bipyramidal symmetry. Among them, three are arranged in trigonal plane and the remaining two orbitals are present above and below the trigonal plane at right angles. The sp³d hybrid orbitals have 20% 's', 60% 'p' and 20% 'd' characters.

Example: PCl₅

• The ground state electronic configuration of phosphorus atom is: 1s² 2s²2p⁶ 3s²3p_x¹3p_y¹3p_z¹. 

• The formation of PCl₅ molecule requires 5 unpaired electrons. Hence the phosphorus atom undergoes excitation to promote one electron from 3s orbital to one of empty 3d orbital.

• Thus the electronic configuration of 'P' in the excited state is 1s² 2s²2p⁶ 3s²3p_x¹3p_y¹3p_z¹ 3d¹.

• In the excited state, intermixing of a 3s, three 3p and one 3d orbitals to give five half filled sp³d hybrid orbitals, which are arranged in trigonal bipyramidal symmetry.

• i.e., Three orbitals are arranged in trigonal planar symmetry, whereas the remaining two are arranged perpendicularly above and below this plane. 

• By using these half filled sp³d orbitals, phosphorous forms five σ_sp3_d-p bonds with chlorine atoms. Each chlorine atom makes use of half filled 3p_z orbital for the bond formation. 

• The shape of PCl₅ molecule is trigonal bipyramidal with 120^o and 90^o of ∠Cl - P - Cl bond angles.