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

Step-by-step solution

The magnitude of crystal field splitting energy ( _o ) depends on the oxidation state of the metal, the nature of the metal ion (3d vs 4d vs 5d series), and the strength of the ligand. Comparing (A) and (B): Both have the same metal and ligand, but Co³⁺ has a higher oxidation state than Co²⁺ . A higher oxidation state leads to a larger _o . Thus, (A) Comparing (B) and (C): Both have the same oxidation state (+3) and ligand, but Rh is a 4d metal while Co is a 3d metal. The _o value increases by about 30% to 50% upon