Tag: the world of carbon

In diamond, each carbon atom is covalently bonded to four other carbon atoms, leaving no free electrons available to conduct electricity.

Diamond is transparent, hard and poor conductor of electricity. In-fact, diamond is hardest known substance on earth. The hardness is due to the presence of strong covalent bonds between C atoms. Hence, the option (B) is the correct answer.

Graphite is an allotrope of carbon. Each carbon is covalently bobded to other three carbon atoms, it contains layers of carbon. The layers slid over each other easily because of the weak Van der Walls' forces between them.

Fullerene is an allotrope of carbon in the form of hollow sphere and called as buckyballs. $C-60$ is the crystalline form and is used as semiconductor.

Crystal density of graphite is $2.266 g/cm^3$ as compared with $3.53 g/cm^3$ for diamond.
In the graphite structure, only three of the four valence electrons of carbon form regular covalent bonds with adjacent carbon atoms.

C-60 is the most stable form and it led the scientists to the conclusion that the cluster must be a spheroidal closed cage in the form of icosahedron.

The first fullerene was discovered in 1985 by Sir Harold W.Kroto, Smalley and Robert F.Curl. They obtained a cage like molecules composed of 60 carbon atoms.

60 carbon atoms are joined together by single and double bonds to form a hollow sphere with 12 pentagonal and 20 hexagonal faces, a design that resembles a football.

Diamond is an allotrope of carbon and it is present in pure form since it contains carbon atoms tetrahedrally bonded to each other.

The  statement C is  true for graphite.
(a) In graphite, each carbon atom is bonded to three other carbon atoms.
(b) Graphite is soft.
(c) It is a good conductor of electricity as delocalised electrons are free to move in delocalised molecular orbitals.