Question

Arrange the following ions in order of decreasing ionic radii: $L{i}^{2+},H{e}^{+},B{e}^{3+}.$

• A. $L{i}^{2+}>H{e}^{+}>B{e}^{3+}$
• B. $L{i}^{2+}<H{e}^{+}<B{e}^{3+}$
• C. $H{e}^{+}>L{i}^{2+}>B{e}^{3+}$
• D. All are same

Answer 1

The correct option is C $H{e}^{+}>L{i}^{2+}>B{e}^{3+}$

$L{i}^{2+},H{e}^{+},B{e}^{3+}$ are all isoelectronic ions. Among isoelectronic ions, ionic radius decreases as the positive charge increases. Therefore, the ionic radii decrease in the order:
$H{e}^{+}>L{i}^{2+}>B{e}^{3+}$