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EEJ MAIN Chemistry QUESTION #5550
Question 1
Identify the set that contains only isoelectronic species (same number of electrons):
  • $O^-,\ F^-,\ Na,\ Mg^+$
  • $O^{2-},\ F^-,\ Na,\ Mg^{2+}$
  • $O^-,\ F^-,\ Na^+,\ Mg^{2+}$
  • $O^{2-},\ F^-,\ Na^+,\ Mg^{2+}$āœ”ļø
Correct Answer Explanation
Each species must have the same electron count. $O^{2-}$: 10 eā». $F^-$: 10 eā». $Na^+$: 10 eā». $Mg^{2+}$: 10 eā». All have 10 electrons ā€” they are isoelectronic! The other options contain species with different electron counts.