AP Chemistrymediummcq1 pt
The ions O²⁻, F⁻, Na⁺, and Mg²⁺ each contain exactly ten electrons. Which of them is smallest?
A.Mg²⁺
B.O²⁻
C.F⁻
D.Na⁺
Explanation
Core Concept
With ten electrons apiece, electron-electron repulsion is identical across the series, so nuclear charge decides size. Magnesium's twelve protons pull hardest on the shared electron cloud, contracting it the most. Radius therefore shrinks steadily from O²⁻ through F⁻ and Na⁺ down to Mg²⁺.
Correct Answer
AMg²⁺
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