The thermodynamic stability of a coordination compound in aqueous solution is quantitatively expressed by its overall formation constant ( ). Among the given species, which complex ion is expected to have the highest formation constant?

Step-by-step solution

The thermodynamic stability of a coordination compound is indicated by its overall formation constant ( ). Higher stability corresponds to a higher formation constant. Among the given ligands, ethylenediamine ( en ) is a bidentate ligand, while NH₃ , H₂O , and Cl^- are monodentate ligands. When a bidentate or polydentate ligand coordinates to a metal ion, it forms a ring structure called a chelate ring. The formation of chelate rings significantly increases the stability of the complex compared to similar complexes