Consider the following hexaaqua complexes: (A) [Co(H₂O)₆]²⁺ (B) [Co(H₂O)₆]³⁺ (C) [Rh(H₂O)₆]³⁺ (D) [Ir(H₂O)₆]³⁺ The correct increasing order of their crystal field splitting energy ( ₀ ) is:

Step-by-step solution

Crystal field splitting energy ( ₀ ) depends on the oxidation state of the central metal and the transition series it belongs to. For the same metal and ligand, ₀ increases with an increase in the oxidation state. Thus, ₀ for [Co(H₂O)₆]²⁺ For the same oxidation state and ligand, ₀ increases down the group (from 3d to 4d to 5d series) by about 30% to 50% per step. Thus, ₀ follows the order: Co³⁺ (3d) Combining these trends, the correct increasing order of ₀ is (A) Answer: (A) < (B) < (C) < (D)