question_answer 120)

  Assertion (A) Graphite is a good conductor of electricity however diamond belongs to the category of insulators. Reason (R) Graphite is soft in nature on the other hand diamond is very hard and brittle.  

Answer:

                  (b) Assertion and Reason both are correct but Reason is not correct explanation of Assertion. Correct explanation is that graphite have layered structure with free electrons due to which it is a good conductor of electricity. On the other hand, diamond have tetrahedral arrangement with no unpaired electron. Therefore, diamond is hard and brittle but insulator.