Question

Which one of the following is the smallest cation?

• A. $N{a}^{+}$
• B. $M{g}^{2+}$
• C. $C{a}^{2+}$
• D. $A{l}^{3+}$

Answer 1

The correct option is D

$A{l}^{3+}$

The smallest ionic radius will be a function of a greater gap between the number of protons (higher number) and electrons (lower number). $A{l}^{3+}$ has the highest value for (protons - electrons).