The isoelectronic set of ions is :
Question:

The isoelectronic set of ions is :

1. $\mathrm{N}^{3-}, \mathrm{O}^{2-}, \mathrm{F}^{-}$and $\mathrm{Na}^{+}$

2. $\mathrm{N}^{3-}, \mathrm{Li}^{+}, \mathrm{Mg}^{2+}$ and $\mathrm{O}^{2-}$

3. $\mathrm{F}^{-}, \mathrm{Li}^{+}, \mathrm{Na}^{+}$and $\mathrm{Mg}^{2+}$

4. $\mathrm{Li}^{+}, \mathrm{Na}^{+}, \mathrm{O}^{2-}$ and $\mathrm{F}^{-}$

Correct Option: 1

Solution:

Atomic numbers of $\mathrm{N}, \mathrm{O}, \mathrm{F}$ and $\mathrm{Na}$ are $7,8,9$ and 11 respectively. Therefore, total number of electrons in each of $\mathrm{N}^{3-}, \mathrm{O}^{2-}, \mathrm{F}^{-}$, and $\mathrm{Na}^{+}$are 10 and hence they are isoelectronic.