AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Students should be able to explain the properties of diamond in terms of…
Full specification wording
Diamond: 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.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 2 of 2
Study notes
From the checked teaching notes for this specification point.
The idea
Diamond is a giant covalent lattice of carbon atoms. Every carbon atom forms four single covalent bonds, arranged tetrahedrally, so each atom is joined to four others and the whole crystal is one continuous network. There are no separate molecules and no free electrons. Melting requires breaking many strong covalent bonds, so the melting point is extremely high. Those same strong bonds resist deformation, making diamond very hard. Because all four outer electrons per carbon are locked into bonding, there are no delocalised electrons, so diamond does not conduct electricity. A useful method is to link each property to a structural feature: high melting point to many strong covalent bonds; hardness to a rigid three-dimensional network; non-conduction to the absence of delocalised electrons.
What earns the marks
- Diamond is a giant covalent (macromolecular) lattice in which each carbon atom is covalently bonded to four other carbon atoms.
- The bonds are strong single covalent bonds arranged tetrahedrally, giving a rigid three-dimensional network with no separate molecules.
- A very large amount of energy is needed to break the many strong covalent bonds, so diamond has a very high melting point.
- The rigid network of strong bonds makes diamond extremely hard, which is why it is used in cutting tools and drill tips.
- All four outer electrons of each carbon atom are used in bonding, so there are no delocalised electrons and diamond does not conduct electricity.
- A good answer links each property explicitly to a structural feature rather than listing properties alone.
Common mistakes and how to put them right
Saying diamond is made of small molecules.
Put it right by stating it is a giant covalent lattice with no separate molecules.
Claiming diamond conducts electricity because it contains carbon.
Put it right by explaining that all outer electrons are localised in covalent bonds, so there are no delocalised electrons.
Stating that diamond is hard because the bonds are short.
Put it right by linking hardness to the rigid three-dimensional network of strong covalent bonds.
Exam tips
- For each property you give, immediately state the structural reason, for example high melting point because many strong covalent bonds must be broken.
- Use precise terms such as giant covalent lattice, tetrahedral and delocalised electrons rather than vague words like strong structure.
- If asked to compare with graphite, refer back to the stem so your answer stays focused on diamond's structure and bonding.
Try the lesson
The start of the Diamond: Students should be able to explain the properties of diamond in terms of its structure and bonding. lesson, made from checked teaching notes for this specification point.
Have a go first
In diamond, each carbon atom is joined to four other carbon atoms by strong covalent bonds. What name is given to this type of giant structure?
Listen
Diamond is a giant covalent lattice of carbon atoms. Every carbon atom forms four single covalent bonds, arranged tetrahedrally, so each atom is joined to four others and the whole crystal is one continuous network. There are no separate molecules and no free electrons. Melting requires breaking many strong covalent bonds, so the melting point is extremely high. Those same strong bonds resist deformation, making diamond very hard. Because all four outer electrons per carbon are locked into bonding, there are no delocalised electrons, so diamond does not conduct electricity. A useful method is to link each property to a structural feature: high melting point to many strong covalent bonds; hardness to a rigid three-dimensional network; non-conduction to the absence of delocalised electrons. A strong answer earns marks for these points. Diamond is a giant covalent (macromolecular) lattice in which each carbon atom is covalently bonded to four other carbon atoms. The bonds are strong single covalent bonds arranged tetrahedrally, giving a rigid three-dimensional network with no separate molecules. A very large amount of energy is needed to break the many strong covalent bonds, so diamond has a very high melting point. The rigid network of strong bonds makes diamond extremely hard, which is why it is used in cutting tools and drill tips. A common slip: Saying diamond is made of small molecules. Instead, stating it is a giant covalent lattice with no separate molecules. Exam tip: For each property you give, immediately state the structural reason, for example high melting point because many strong covalent bonds must be broken.
See it
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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