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Ionic Radius

Mediumchemistry

An isoelectronic series contains O2-, F-, Na+ and Mg2+. Which species has the smallest ionic radius?

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About This Question

Subject
chemistry
Chapter
classification of elements and periodicity in properties
Topic
ionic radius
Difficulty
Medium
Year
2025
Tags
IsoelectronicIonic RadiusNuclear Charge

Solution

Correct Answer:

Mg2+

All four ions have 10 electrons, so size depends mainly on nuclear charge. Greater nuclear charge pulls the same electron cloud more strongly and decreases radius. Since Mg2+ has the highest proton number (12), it has the smallest ionic radius among these ions.

This medium difficulty chemistry question is from the chapter classification of elements and periodicity in properties, covering the topic of ionic radius. It appeared in the 2025 exam.

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