Identify the species with the largest ionic radius among the following isoelectronic ions: ${\text{N}}^{3-},{\text{O}}^{2-},{\text{F}}^{-},{\text{Na}}^{+},{\text{Mg}}^{2+}$.

Solution

1. All given ions have 10 electrons, making them isoelectronic.
2. The ionic radius of isoelectronic species is inversely proportional to the atomic number ($Z$).
3. Nitrogen has the lowest atomic number ($Z=7$) among the given species.
4. Therefore, ${\text{N}}^{3-}$ has the largest ionic radius.
5. Hence the answer is (A).