MHT CET202520 Apr 2025Morning ShiftChemistryCoordination CompoundsActual
Identify the correct decreasing order of stability of complexes formed by divalent metal ions with same ligand.
Options
- ACu ²⁺> Mn ²⁺> Cd ²⁺
- BCd ²⁺> Mn ²⁺> Cu ²⁺
- CMn ²⁺> Cd ²⁺> Cu ²⁺
- DCu ²⁺> Cd ²⁺> Mn ²⁺
Correct answer
A. Cu ²⁺> Mn ²⁺> Cd ²⁺
Step-by-step solution
Stability in the Irving-Williams series: For first-row transition metal divalent ions, complex stability follows Mn ²⁺ Zn ²⁺ , so Cu ²⁺ > Mn ²⁺ . Comparison of Mn ²⁺ and Cd ²⁺ : Both have zero crystal field stabilization energy, but Mn ²⁺ has a smaller ionic radius (83 pm) than Cd ²⁺ (95 pm), resulting in higher charge density and stronger ligand interactions. Thus, Mn ²⁺ > Cd ²⁺ . Combined order: Cu ²⁺ > Mn ²⁺ > Cd ²⁺ , corresponding to option A.