Given below are two statements: Assertion (A): Melting point of Boron () is unusually high in group elements. Reason (R): Solid Boron has very strong crystalline lattice. In the light of the above statements, choose the most appropriate answer from the options given below:
Both (A) and (R) are correct but (R) is not the correct explanation of (A)
Both (A) and (R) are correct and (R) is the correct explanation of (A)
(A) is true but (R) is false
(A) is false but (R) is true
Correct answer:B
Standard Method
Given: Assertion (A): Melting point of Boron is and is unusually high in group elements.
Find: Whether Assertion (A) and Reason (R) are true, and whether Reason (R) correctly explains Assertion (A).
Boron has a much higher melting point than the other group elements, so Assertion (A) is true.
Solid boron has a strong crystalline covalent network lattice. Breaking this extensive lattice requires a large amount of energy, so Reason (R) is also true.
Since the strong crystalline lattice is the cause of the unusually high melting point, Reason (R) correctly explains Assertion (A).
Therefore, both (A) and (R) are correct and (R) is the correct explanation of (A). The correct option is B.
Detailed Logical Analysis
Given: Two statements about boron in group elements.
Find: The correct assertion-reason relationship.
Hence, Reason (R) correctly explains Assertion (A).
So, the correct answer is Both (A) and (R) are correct and (R) is the correct explanation of (A), that is, option B.
Assuming that a high melting point in boron is due only to metallic character is incorrect because boron is not a typical metal in group . Its unusually high melting point arises from its strong covalent crystalline network, so focus on bonding and lattice structure instead.
Treating the Reason (R) as merely an associated fact and not an explanation is wrong because the strong crystalline lattice directly causes the high melting point. Always check whether the reason gives the physical basis of the assertion.
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