Statement I: After splitting of d-orbitals during complex formation, the orbitals form two sets t_2g and e_g

Statement II: Splitting of d-orbitals occur only in the case of strong field ligands such as CN⁻

Statement I is correct but Statement II is false

The correct answer is option 3. Statement I is correct, but Statement II is false.

Statement I: After splitting of d-orbitals during complex formation, the orbitals form two sets t_2g and e_g.

Statement I is correct. During complex formation, the d-orbitals of the central metal ion are split into two sets of different energies. The lower energy set is called t_2g (three orbitals), and the higher energy set is called eg (two orbitals). This splitting occurs due to the interaction of the d-orbitals with the ligand's electric field.

Statement II: Splitting of d-orbitals occurs only in the case of strong-field ligands such as CN⁻.

Statement II is false. The splitting of d-orbitals, known as crystal field splitting or ligand field splitting, occurs not only in the case of strong-field ligands but also in the case of weak field ligands. Both strong and weak field ligands can induce splitting of the d-orbitals, but the magnitude of splitting differs. Strong field ligands cause larger splitting, resulting in more distinct t_2g and eg sets, while weak field ligands cause smaller splitting with less energy difference between t_2g and e_g orbitals.