Statement I: Under the strong field ligand only the degeneracy of the d-orbitals is lost
Statement II: After splitting of the d-orbitals also Hund’s rule is not violated anywhere
Answer & explanation
Correct answer: option 1
The answer is (1) Both Statement I and statement II are correct and statement II is the correct explanation of statement I.
Statement I is correct because in a strong field ligand, the d-orbitals are split into two groups, with the lower energy group being more stable than the higher energy group. This splitting of the d-orbitals is called the crystal field splitting.
Statement II is also correct because Hund's rule states that electrons will occupy degenerate orbitals singly before they start pairing up. However, in a strong field ligand, the lower energy d-orbitals are so much more stable than the higher energy d-orbitals that the electrons will occupy the lower energy d-orbitals singly, even if this means that some of the d-orbitals are not fully occupied.
The reason why Statement II is the correct explanation of Statement I is because the splitting of the d-orbitals in a strong field ligand is what allows Hund's rule to be violated. If the d-orbitals were not split, then the electrons would have to occupy all of the d-orbitals singly before they could start pairing up. However, because the lower energy d-orbitals are so much more stable, the electrons will occupy these orbitals singly, even if this means that some of the d-orbitals are not fully occupied.