The statement(s) that are correct about the species O2-, F-, Na+ and Mg2+: (A) All are isoelectronic (B) All have the…

🧠 Isoelectronic = same electrons. It does NOT mean same nuclear charge — that is the catch in statement (B) $\ce{O^{2-}}$, $\ce{F^-}$, $\ce{Na^+}$, $\ce{Mg^{2+}}$ each have 10 electrons but very different proton counts (8, 9, 11, 12). The four statements test whether you grasp this distinction.

🗺️ Check each statement (A) All are isoelectronic — count electrons: $8+2$, $9+1$, $11-1$, $12-2$, all give 10. True. (B) All have the same nuclear charge — Z values are 8, 9, 11, 12. All different. False. (C) $\ce{O^{2-}}$ has the largest ionic radius — lowest Z (8) means weakest pull on the same 10 electrons → biggest. True. (D) $\ce{Mg^{2+}}$ has the smallest ionic radius — highest Z (12) means strongest pull → smallest. True.

Correct statements: A, C, D.

⚠️ The trap Statement (B) is the classic confusion. Isoelectronic literally means "same electrons", not "same charge". Many students assume isoelectronic species share everything — same size, same charge, same Z. They share only the electron count. Everything else can differ.

$\boxed{\text{Answer: (c)}}$