Question

Discuss the structures of diamond. How would you explain the properties of these substances on the basis of their structures?

Answer 1

Structure of Diamond

1. Diamond is an allotrope of carbon.
2. A diamond is made up of many three-dimensional networks of carbon atoms that are joined together by strong covalent bonds.
3. Each carbon atom in diamond is sp³ hybridised.
4. Each carbon atom is tetrahedrally bonded to four other carbon atoms.
5. It forms a three-dimensional giant covalent network extending in all directions.
6. All bonds in the network are strong covalent σ-bonds.
7. All C−C bonds are equivalent to 154 pm (1.54 Å) and have a C−C−C bond angle of 109°28’.
8. Each carbon atom lies at the center of a regular tetrahedron with carbon atoms at the corners.

Properties of Diamond

1. Diamond is extremely hard, the hardest natural substance.
2. It has a very high melting point of 3843 K.
3. The density of diamond is 3.51 g/cm³.
4. It is insoluble in all solvents.
5. Diamond is a non-conductor of electricity.
6. It is transparent and allows light to pass through.
7. It has a high refractive index of 2.45, giving it brilliance.
8. It is chemically resistant to acids, bases, and salts.
9. It reacts with fused sodium carbonate.
10. It is oxidised to CO₂ when heated with K₂Cr₂O₇ + H₂SO₄ at 475 K.
11. The value of a diamond depends on its size and colour.
12. Bluish-white diamonds are the most valuable.
13. Yellowish diamonds are less valuable.
14. Black diamonds are the least valuable and used in industry.