Consider the following octahedral complexes: (A) [ Co ( C ₂ O ₄)₃]³⁻ (B) [ Fe ( CN )₆]³⁻ (C) [ CoF ₆]³⁻ (D) [ Cr ( H ₂ O )₆]³⁺ The correct increasing order of the number of electrons in their t_ 2g orbitals is:

Step-by-step solution

For (A) [ Co ( C ₂ O ₄)₃]³⁻ : Co is in +3 oxidation state ( 3d^6 ). Oxalate ( C ₂ O ₄²⁻ ) acts as a strong field ligand for Co ³⁺ , resulting in a low-spin complex. Configuration is t_ 2g ^6 e_g^0 . Number of t_ 2g electrons = 6. For (B) [ Fe ( CN )₆]³⁻ : Fe is in +3 oxidation state ( 3d^5 ). CN ⁻ is a strong field ligand, resulting in a low-spin complex. Configuration is t_ 2g ^5 e_g^0 . Number of t_ 2g electrons = 5. For (C) [ CoF ₆]³⁻ : Co is in +3 oxidation state ( 3d^6 ). F ⁻ is a weak field ligand, resulting