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Given below are two statements : one is labelled as - Assertion (A) and the other is labelled as Reason (R). Assertion (A) : The ionic radii of O2− and Mg2+ are same. Reason (R) : Both O2− and Mg2+ are isoelectronic species. In the light of the above statements, choose the correct answer from the options given below.

1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. (A) is false but (R) is true.

Correct answer: (A) is false but (R) is true.

Solution

The assertion is incorrect because while O2− and Mg2+ are isoelectronic, their ionic radii differ due to the different nuclear charges affecting the attraction between the nucleus and the electrons. The reason is correct as both ions have the same electron configuration, but this does not justify the assertion.

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