Question

Graphite is a ⋯⋯ conductor of electricity whereas diamond is a ⋯⋯ conductor of electricity.
(A) bad, bad
(B) good, bad
(C) bad, good
(D) good, good

Answer 1

The ability to conduct electricity depends on the electrons which are available for conductance. Among the given options one material has free electrons which are delocalized between the layers. If free electrons are present then the material would be a good conductor and vice versa.

Complete step by step solution:
- Diamond and graphite are two examples of allotropes of carbon. As we know, allotropy is the property of existence of some chemical elements in two or more different forms.
- Since the arrangement of atoms vary in allotropes, their properties also vary accordingly.
- In the case of diamonds, the carbon atoms are arranged in a lattice, which is a variation of the face-centered cubic crystal structure. The reason for the physical qualities of diamonds can be attributed to the strong covalent bonding between its atoms. In diamond, each carbon atom is covalently bonded to four other carbons as in a tetrahedron.
- The tetrahedrons in diamond together form a three-dimensional network in the chair conformation of six-membered carbon rings. This strong network of hexagonal rings and covalent bonds are the reason for the strong hard nature of diamonds.
- As we mentioned graphite is another allotrope of carbon. It has a planar, layered structure. It consists of each layer in which the carbon atoms are arranged in a hexagonal lattice. This allotrope of carbon has two known forms, α (hexagonal) and β (rhombohedral) and they have very similar physical properties.
- We asked to find out about the electrical conductance of these allotropes. As we know, four electrons are present in the outer shell of a carbon atom. As we mentioned above, in diamond, each of these outer shell electron forms a covalent bond in a tetrahedral arrangement and hence there are no free electrons available for the conduction of electricity.
- In the case of graphite, it has hexagonal arrangement in which only three electrons out of four outer shell electrons form covalent bonds and thus it leaves one free electron. This free or delocalized electron can travel freely between the layers of carbon in graphite and thus it can conduct electricity.

Therefore, the answer is option (B). That is graphite is a good conductor of electricity whereas diamond is a bad conductor of electricity.

Note: Do not confuse graphene with graphite. It is a single layer of graphite or can be also described as the basic structural element of carbon allotropes. It acts as zero-gap semiconductor which allows it to display high electron mobility at room temperature. It's a comparatively new material which has extraordinary thermal, electrical, and physical properties.