Diamond — AQA GCSE Chemistry
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Diamond explained
Diamond covers 2 specification points, including In diamond, each carbon atom forms four… and Students should be able to explain the….
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Open a point below for its explanation and revision guidance.
In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard, has a very high melting point and does not conduct electricity.
Diamond is a giant covalent structure made only of carbon atoms. Each carbon atom forms four strong covalent bonds to four other carbon atoms, arranged tetrahedrally. This means every carbon atom is bonded to four neighbours, producing a rigid three-dimensional network that extends throughout the crystal. A large amount of energy is needed to break these many strong covalent bonds, so diamond has a very high melting point. The rigid network also makes diamond extremely hard, which is why it is used in cutting tools and drill bits. In diamond, all four outer electrons of each carbon atom are used in covalent bonding, so there are no delocalised electrons or free ions. As a result, diamond does not conduct electricity.
Students should be able to explain the properties of diamond in terms of its structure and bonding.
Diamond is a giant covalent lattice of carbon atoms. Each carbon atom forms four single covalent bonds to four other carbon atoms, arranged tetrahedrally. Because each bond is shared between two atoms, the ratio of atoms to bonds is 1:2 and every outer electron is localised in a bond. This rigid three-dimensional network has no separate molecules and no free electrons or ions. Consequently diamond has a very high melting point because many strong covalent bonds must be broken, it is extremely hard because the lattice resists deformation, and it does not conduct electricity because there are no delocalised electrons or ions to carry charge. For example, this explains its use in cutting tools and drill tips.
Your focus
- Describe the structure of diamond as a giant covalent lattice with four covalent bonds per carbon atom.
- Explain why diamond is very hard and has a very high melting point.
- Explain why diamond does not conduct electricity in terms of the absence of mobile charge carriers.
Show all 6 objectives
- Describe the giant covalent lattice structure of diamond, including four covalent bonds per carbon atom.
- Explain why diamond has a very high melting point and is extremely hard.
- Explain why diamond does not conduct electricity in terms of localised electrons.
Diamond exam tips
Marking Points
- Diamond is a giant covalent structure in which each carbon atom forms four covalent bonds to other carbon atoms.
- The carbon atoms are arranged in a rigid three-dimensional network, which makes diamond very hard.
- Many strong covalent bonds must be broken to melt diamond, so it has a very high melting point.
- All outer electrons are used in covalent bonding, so there are no delocalised electrons or free ions to carry charge.
- Because there are no mobile charge carriers, diamond does not conduct electricity.
- States that each carbon atom in diamond forms four covalent bonds to four other carbon atoms.
- Describes the arrangement as a giant covalent lattice or tetrahedral network with no separate molecules.
- Links the high melting point to the many strong covalent bonds that must be broken.
- Links the extreme hardness to the rigid three-dimensional network of strong covalent bonds.
- Explains that diamond does not conduct electricity because all outer electrons are localised in covalent bonds, so there are no delocalised electrons or ions.
Examiner Tips
- 💡State the number of covalent bonds per carbon atom and link this to the giant rigid structure.
- 💡Explain hardness and high melting point by referring to the strong covalent bonds throughout the network.
- 💡Explain electrical non-conduction by stating that there are no delocalised electrons or free ions.
- 💡Name the structure first, then link each property to a structural feature in a because clause.
- 💡Use the phrase many strong covalent bonds must be broken when explaining the high melting point.
- 💡State explicitly that there are no delocalised electrons or ions when explaining why diamond does not conduct electricity.
Common Mistakes
- Saying that diamond conducts electricity because it contains carbon; carbon alone does not guarantee conduction, and diamond has no delocalised electrons.
- Stating that diamond has a high melting point because of weak intermolecular forces; in a giant covalent structure, strong covalent bonds must be broken.
- Describing diamond as a molecule; it is a giant covalent lattice, not a simple molecular substance.
- Saying diamond is made of small molecules: correct this by describing a giant covalent lattice with no separate molecules.
- Saying diamond conducts electricity because it contains carbon: correct this by stating that all four outer electrons per carbon are localised in covalent bonds, so there are no delocalised electrons.
- Saying diamond has a high melting point because covalent bonds are weak: correct this by stating the bonds are strong and many must be broken.