Combination of 1s, 3p and 1d orbital result in the formation of sp3d orbital in which three
lobes are oriented towards the corners of a triangle and the other lie perpendicular to them to minimize the repulsions.
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: PF5
In PF5, one of the electrons in 3s orbital is promoted to the higher 3d orbital so that it has five unpaired electrons. These five orbitals hybridize to form five sp3d hybrid orbitals, which adopt trigonal bipyramidal arrangement. Each of the sp3d hybrid orbitals overlaps with 2p orbital of fluorine forming five P–F bonds
Structure of PF5