Question

Which of the following factors tend to increase the stability of metal ion complexes?
A.Higher ionic radius of the metal ion
B.Higher charge/ size ratio of the metal ion
C.Lower ionization potential of the metal ion
D.Lower basicity of the ligand

Answer 1

Hint: To answer this question you must recall the general properties of complexes. The central metal atom is linked to ligands by donation of pairs of electrons by the ligands to the central metal atom.

Complete step by step answer:
In coordination complexes, the cations with higher oxidation states result in the formation of more stable complexes with common ligands like ammonia or water. Also, with a decrease in the size of the metal cation, the stability of these metal complexes increases.
Thus, we can rule out option A as it says that the stability increases with higher ionic radius.
Stability of a coordination complex increases with an increase in charge density. More is the charge density on the metal ion, more strongly will the ligand be attached to the central metal ion and thus resulting in increased stability. So, option B is correct.
The complex stability depends on the nature of the ligand as, the more easily the ligand can donate its electron pair, the greater is the stability of the complex. Thus, we can say that for higher stability of the complex, ligand should be more basic. Hence, we can rule out option D. Chelating the effect of ligands also increases the stability of metal ion complexes.

Thus, the correct option is B.

Note:
Complex compounds are formed in several steps where each step is reversible. The stability of metal ion complexes varies due to various factors, namely the nature of ligands, charge on the metal ion and the size of the metal ion.