→ The Crystal Field Theory (CFT) is an electrostatic model which considers the metal- ligand bond to be ionic arising purely from electrostatic interactions between the metal ion and the ligand.
→ Ligands are treated as point charges in case of anions or point dipoles in case of neutral molecules.
→ The five d orbitals in an isolated gaseous metal atom/ion have same energy, i.e., they are degenerate.
→ This degeneracy is maintained if a spherically symmetrical field of negative charges surrounds the metal atom/ion.
→ However, when this negative field is due to ligands (either anions or the negative ends of dipolar molecules like NH3 and H2O) in a complex, it becomes asymmetrical and the degeneracy of the d orbitals is lifted.
→ It results in splitting of the d orbitals.
→ The pattern of splitting depends upon the nature of the crystal field.