MHT CET202615 April 2026Evening ShiftChemistryCoordination CompoundsActual
Identify the complex having the highest number of unpaired electrons from following.
Options
- A[ Co(NH ₃)₆]³⁺
- B[ CoF ₆]³⁻
- C[ NiCl ₄]²⁻
- D[ Ni(CN) ₄]²⁻
Correct answer
B. [ CoF ₆]³⁻
Step-by-step solution
In [ Co(NH ₃)₆]³⁺ , Co is in +3 oxidation state with 3d^6 configuration. Since NH₃ acts as a strong field ligand for Co ³⁺ , pairing of electrons takes place resulting in t_ 2g ^6 e_g^0 configuration. Number of unpaired electrons = 0 . In [ CoF ₆]³⁻ , Co is in +3 oxidation state with 3d^6 configuration. F ^- is a weak field ligand, so no pairing occurs. The configuration is t_ 2g ^4 e_g^2 . Number of unpaired electrons = 4 . In [ NiCl ₄]²⁻ , Ni is in +2 oxidation state with 3d^8 configuration. Cl ^- is a weak field