Which from following elements is isoelectronic with $\mathrm{Na}^{+}$?

Which from following elements is isoelectronic with $\mathrm{Na}^{+}$?
  1. F
  2. $\mathrm{O}$
  3. $\mathrm{Mg}$
  4. $\mathrm{Ne}$

Solution

Atoms and ions having the same number of electrons are isoelectronic. \begin{array}{|c|c|} \hline Species & No. of electrons \\ \hline \mathrm{Na}^{+} & 11-1=10 \\ \hline \mathrm{F} & 9 \\ \hline \mathrm{O} & 8 \\ \hline \mathrm{Mg} & 12 \\ \hline \mathrm{Ne} & 10 \\ \hline \end{array}

Asked in: MHT CET 2023 (11 May Shift 2)

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