JEE MainChemistryp Block Elements (Group 13 & 14)
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Boron has an exceptionally high melting point compared to other members of Group 13. Reason (R): Solid boron exists as a giant polymeric structure with strong covalent bonds forming B ₁₂ icosahedral units. In the light of the above statements, choose the most appropriate answer from the options giv
Options
- ABoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- BBoth (A) and (R) are correct and (R) is the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
B. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
Boron is a non-metal and exists as a giant covalent polymeric structure consisting of B ₁₂ icosahedral units. Due to the presence of very strong covalent bonds in this three-dimensional network, an exceptionally large amount of thermal energy is required to break the lattice. Consequently, boron has an unusually high melting point (approx 2453 K) compared to the rest of the Group 13 elements. Thus, both Assertion (A) and Reason (R) are correct, and (R) is the correct explanation for the high melting point mentioned