CBSE 2026 · Region 1 · Set 2 · Q14 · 1 mark
Assertion (A) : Actinoids show irregularities in their electronic configurations.
Reason (R) : In actinoids 5f, 6d and 7s orbitals are of comparable energies.
Official answer
From CBSE’s own marking scheme for this paper.
(B)
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
The d-and f-Block ElementsThe ActinoidsUnderstandassertion_reasonmedium
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CBSE Class 12 Chemistry past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.