According to this theory, the metal atom or ion under the influence of
ligands can use its (n-1)d, ns, np or ns, np, nd orbitals for hybridisation
to yield a set of equivalent orbitals of definite geometry such as octahedral,
tetrahedral, square planar and so on (Table 5 2) These hybridised orbitals
are allowed to overlap with ligand orbitals that can donate electron pairs
for bonding This is illustrated by the following examples