28.3.2—d-orbital splitting

Ligand-field splitting removes the equality of the five d-orbital energies. In an octahedral complex, two orbitals point towards ligands and rise in energy while three lie between axes and are lower; in a tetrahedral complex the pattern is reversed, with three higher and two lower.

The separation is ΔE. It is not a new electron shell: it is an energy difference within the same d subshell, created by the ligand arrangement around the metal.

For an octahedral ion, the dxy, dxz and dyz orbitals form the lower set, while dz² and dx²−y² form the upper set. A tetrahedral diagram must show the opposite 3:2 ordering.

Do not copy the octahedral diagram for a tetrahedral complex, or treat “higher” and “lower” as absolute energies independent of the complex.