Select the correct assumptions in Crystal Field Theory (CFT) from the following:
(A) Ligands are treated as point charge or point dipole.
(B) The five d orbitals in an isolated gaseous metal atom are non-degenerate
(C) Degeneracy of the d orbitals is restored with the approach of ligand towards metal
(D) Metal-ligand bond is ionic arising purely from electrostatic interactions
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) and (D) only
Crystal field theory (CFT) is an electrostatic model of bonding in complexes. It looks at how the negative field of the ligands changes the energies of the five d orbitals of the metal.
(A) Ligands are treated as point charge or point dipole. — Correct. Anionic ligands (Cl−, CN−) are taken as point charges, and neutral ligands (NH3, H2O) as point dipoles whose negative end faces the metal.
(B) The five d orbitals in an isolated gaseous metal atom are non-degenerate — Incorrect. In an isolated gaseous atom or ion there is no field around the metal, so all five d orbitals have the same energy: they are degenerate.
(C) Degeneracy of the d orbitals is restored with the approach of ligand towards metal — Incorrect. The approach of the ligands makes the field around the metal asymmetrical. The d orbitals pointing towards the ligands are repelled more than the others, so the degeneracy is lifted and the d orbitals split (into t2g and eg in an octahedral field). Nothing is restored.
(D) Metal-ligand bond is ionic arising purely from electrostatic interactions — Correct. CFT treats the metal–ligand bond as purely ionic, an attraction between the positive metal ion and the negative ligands, with no covalent sharing of electrons.
NCERT (2026-27 edition):
Crystal Field Theory – “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.”