Question

Which is the correct order for ionic radii?

• A.
• B.
• C.
• D. None of the above

Answer 1

The correct option is A

$L{i}^{+}\Rightarrow 1s^2$

$A{l}^{3+}\Rightarrow 1s^{2}2s^{2}2p^6$
$M{g}^{2+}\Rightarrow 1s^{2}2s^{2}2p^6$

$K^{+}\Rightarrow 1s^{2}2s^{2}2p^{6}3s^{2}3p^6$

Principal quantum number ($n$) is maximum in $K^{+}$, there it is maximum in size. $A{l}^{3+}$ and $M{g}^{2+}$ are isoelectronic.

$\therefore$ $A{l}^{3+}<M{g}^{2+}$ and for $Li+$ it is least