Class NEET 2026 ALL Q #1985
COMPETENCY BASED
APPLY
4 Marks 2026 NTA-RE-NEET-2026 MCQ SINGLE
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Generally, 3d transition metals have high melting points. Reason R: Involvement of 3d-electrons in addition to 3s-electrons in the interatomic metallic bonding. In light of the above statements, choose the most appropriate answer from the options given below:
(A) A is not correct but R is correct
(B) Both A and R are correct and R is the correct explanation of A
(C) Both A and R are correct and R is NOT the correct explanation of A
(D) A is correct but R is not correct.
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Correct Answer: B

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Detailed Solution

Step 1: Analyze Assertion A

Transition metals (d-block elements) exhibit high melting points due to strong interatomic metallic bonding. This bonding arises from the overlap of d-orbitals, which provides a greater number of electrons for delocalization compared to s-block elements.

Step 2: Analyze Reason R

The reason states that 3d-electrons are involved in metallic bonding in addition to 3s-electrons. This is factually incorrect. In 3d transition metals, the valence shell is 4s, not 3s. The metallic bonding involves the participation of (n-1)d and ns electrons. Specifically, for the first transition series, it is the 3d and 4s electrons that contribute to the metallic bond strength.

Step 3: Conclusion

Since the Assertion is correct regarding the high melting points, but the Reason incorrectly identifies the electron shells involved (citing 3s instead of 4s), the Reason is false.

Final Answer: D

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student must apply knowledge of electronic configuration and metallic bonding principles to evaluate the validity of specific scientific statements.
Knowledge Dimension: CONCEPTUAL
Justification: The question tests the understanding of the relationship between electronic structure and physical properties (melting point) in transition metals.
Syllabus Audit: In the context of NEET, this is classified as COMPETENCY. This question format is standard for the NEET Chemistry section, requiring precise conceptual clarity to distinguish between correct and incorrect scientific reasoning.

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