Among $\mathrm{F^{-}}$, $\mathrm{Na^{+}}$, $\mathrm{O^{2-}}$ and $\mathrm{Mg^{2+}}$ ions, those having the highest and the lowest ionic radii respectively are
(a)$\mathrm{O}^{2-}$ and $\mathrm{Na}^{+}$
(b)$\mathrm{F}^{-}$and $\mathrm{Mg}^{2+}$
(c)$\mathrm{O}^{2-}$ and $\mathrm{Mg}^{2+}$
(d)$\mathrm{Mg}^{2+}$ and $\mathrm{O}^{2-}$
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
All four are isoelectronic (10 e); size falls with nuclear charge: O²⁻ (140 pm) > F⁻ > Na⁺ > Mg²⁺ (72 pm).