Chemistry Classification of Elements and Periodicity JEE ADVANCED Previous Year Question Single Correct MCQ
Published on: August 14, 2026

Assertion: The first ionization energy of Be is greater than that of B.

Reason: 2p orbital is lower in energy than 2s.

A
Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
B
Both Assertion and Reason are true but Reason is not correct explanation of Assertion.
C
Assertion is true but Reason is false.
D
Assertion is false but Reason is true.

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Text Solution

Verified by Experts
The correct answer is:
C

Be has completely filled stable 2s 2 orbital and thus Be has higher ionisation energy than B. 2s orbital has less energy than 2p orbital. (From (n+ λ ) rule)

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