1(g) Covalent bonding
Pearson Edexcel International GCSE Chemistry · 4CH1
Paper 2 | Whole paper: All content including bold C statements
Shared electron pairs, and the crucial distinction between the strong bonds inside a molecule and the weak forces between molecules.
Specification coverage
Topic 1 Principles of chemistry (g) Covalent bonding — statements 1.55–1.60C (includes bold C statements assessed on Paper 2 only)
Assessment objectives: AO1, AO2. Suggested learning time: 60 minutes.
Required knowledge
- The formation of covalent bonds by shared electron pairs
- Dot-and-cross diagrams for simple molecules
- The properties of simple molecular substances: low melting and boiling points, poor conduction
- Giant covalent structures: diamond, graphite and silicon dioxide, and their properties
- Bold C statements: the relationship between structure and properties in greater depth
Required skills
- Distinguish intramolecular bonds from intermolecular forces in an explanation
- Explain the properties of diamond and graphite from their structures
How it is examined
- Multiple-choice and short-answer recall
- Application of the content to an unfamiliar context
- Extended open-response, marked on the quality of a connected explanation
Common mistakes
- Saying simple molecular substances melt at low temperatures 'because the covalent bonds are weak'. The covalent bonds are strong; the forces BETWEEN molecules are weak, and those are what melting overcomes. This is the single most-penalised error in the topic.
- Saying graphite conducts because it has free ions. It has delocalised electrons.
- Forgetting that each carbon in graphite bonds to three others, leaving one electron delocalised.