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Question 840008
JEE Chemistry · Hard

Periodic Table and Periodicity: JEE Main MCQ

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JEE MainHardQuestion 840008

Question

The correct order of ionic radii is:
  1. A
    Na⁺ < Mg²⁺ < Al³⁺ (isoelectronic: more charge = smaller)
  2. B
    Al³⁺ < Mg²⁺ < Na⁺
    Correct
  3. C
    Na⁺ > Mg²⁺ > Al³⁺
  4. D
    All equal for isoelectronic species

Correct answer

Al³⁺ < Mg²⁺ < Na⁺

Explanation

Na⁺, Mg²⁺, Al³⁺ are isoelectronic (10 e⁻ each). For isoelectronic species: higher nuclear charge → smaller ionic radius. Z: Na=11, Mg=12, Al=13. Radius order: Al³⁺ < Mg²⁺ < Na⁺.

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