Question

The sizes of the following species increase in the order

• A. $M{g}^{2+}<N{a}^{+}<F<A1$
• B. $F<A1<N{a}^{+}<M{g}^{2+}$
• C. $A1<M{g}^{2+}<F<N{a}^{+}$
• D. $N{a}^{+}<A1<F^{-}<M{g}^{2+}$

Answer 1

Answer: (A)

$M{g}^{2+},N{a}^{+},F^{-}$ are isoelectronic ions (having two filled orbitals), therefore, their size increase in the order : $M{g}^{2+}<N{a}^{+}<F^{-}$. AI belongs to the 3rd period and also does not carry any charge. Hence it has the largest size.
$\therefore$ Over all sizes increase in the order
$M{g}^{2+}<N{a}^{+}<F^{-}<Al$