Question

Consider the isoelectronic species, $N{a}^{+}$, $M{g}^{2+}$, $F^{-}$ and $O^{2-}$. The correct order of increasing, length of their radii is

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

Answer 1

Answer: (B)

For isoelectronic species, ionic radii decrease with increase in nuclear charge (i.e., no. of protons). Thus, the cation with greater +ve charge will have a smaller radius and the anion with greater -ve charge will have a larger radius. Thus, the correct order of Increasing ionic radii is $M{g}^{2+}<N{a}^{+}<F^{-}<O^{2-}$.