Question

Explain why diamond is harder than graphite. Why is graphite an electrical conductor but diamond is not?

Short answer

Diamond is harder than graphite due to its compact, three-dimensional network structure with strong covalent bonds, whereas graphite is made up of layers of carbon atoms stacked together by weak forces. Graphite is a good conductor of electricity because it has one free electron per atom that can move about freely, while all of diamond's electrons are used for bonding, preventing it from conducting electricity.

Step-by-step solution

Explanation of Diamond and Graphite Structures

Diamond and graphite are both forms of carbon known as allotropes. Diamond has a tetrahedral structure where each carbon atom is covalently bonded to four other carbon atoms. In contrast, graphite is made up of layers of carbon atoms where each atom is bonded to three others, leaving one electron free. The layers are weakly bonded to each other, allowing them to slide over each other easily.

Why Diamond is Harder Than Graphite

The hardness of diamond can be attributed to its compact, three-dimensional network structure where each carbon atom is bonded to four others, forming a rigid tetrahedral structure. The covalent bonds within this structure are very strong, and hence, a lot of energy is required to break them. On the other hand, graphite is composed of two-dimensional layers where each carbon atom is bonded to three others, forming hexagonal rings. These rings are stacked together by weak forces, which are relatively easy to break, leading to graphite being much softer than diamond.

Conductivity of Graphite and Diamond

Graphite induces electrical conductivity as in its structure, each carbon atom has one unbounded 'free' electron. These free electrons are mobile, and can move through the structure, allowing electricity to flow. In a diamond, however, all four outer electrons on each atom are taken up in bonding, and there is no free electron available to conduct electricity, thus it does not.