Define crystal field theory

he valence bond theory could not explain the stability of coordination compounds. It also failed to throw a light on the differences between strong and weak ligands. Therefore, scientists proposed the crystal field theory.

According to this theory, the metal-ligand bond acts as an ionic bond arising purely from the electrostatic interactions between the metal ions and ligands. This theory takes anions as point charges and neutral molecules as dipoles. When the transition metals do not bond to any ligand, their d orbitals degenerate. This means that they have the same amount of energy.

When they start bonding with other ligands, the d orbitals split apart and become non-degenerate. This bonding occurs mainly due to different symmetries of the d orbitals and the inductive effect of the ligands on the electrons. The pattern of the splitting of d orbitals depends on upon the nature of crystal field.