Ligand field theory

Coordination of ligands to a transition metal ion causes the initially degenerate d-orbitals to separate in energy. How exactly they split is determined by the number and spatial arrangement of the ligands about the metal ion. For example, six ligands in regular octahedral array, situated (say) on the x, y, and z axes of a Cartesian co-ordinate system with the metal ion at its centre, split the d-orbitals as follows: