Question

The crystalline forms of carbon are diamond, graphite and __________
(A) Lamp black
(B) Fullerene
(C) Coke
(D) None of these

Answer 1

There are three known crystalline forms of carbon. One of them is named after Buckminster Fuller and is also known as buckminsterfullerene or buckyball. Graphite and diamond are natural allotropes of carbon while buckminsterfullerene was developed artificially in 1985 by researchers at Rice University.

Complete step by step solution:
Carbon shows allotropy. The phenomenon by which an element can exist in more than one physical state is known as allotropy. Carbon is capable of forming many allotropes due to its valency. The allotropes of carbon can be classified into two: 1.) Amorphous carbon allotropes, and 2.) Crystalline carbon allotropes. Diamond and graphite are well known crystalline forms or allotropes of carbon. In recent decades, many more allotropes of carbon have been discovered and researched. One of the allotropes of carbon was discovered in 1985 by Buckminster Fuller and was called buckminsterfullerene or fullerene. It has a football-like structure and thus is also known as a buckyball. Cylindrical fullerenes are also called carbon nanotubes or buckytubes. The discovery of fullerene greatly expanded the number of allotropes of carbon, which had early been limited to diamond, graphite and amorphous carbon such as soot, coke and charcoal.
Therefore, the crystalline forms of carbon are diamond, graphite and fullerene. Thus, the correct option is B, that is, fullerene.

Note: Fullerene molecule consists of carbon atoms connected by single and double bonds or basically, contain $s{p^2}$ carbon atoms. These $s{p^2}$ carbon atoms are in an arrangement of five and six-membered rings. More common and studied fullerenes are ${{\text{C}}_{{\text{60}}}}{\text{ and }}{{\text{C}}_{70}}$ . Nowadays, graphene is also an important allotrope of carbon, consisting of a single layer of carbon atoms arranged in 2-D. It also contains the same type of bonding as seen in fullerene.