Giant Covalent Structures

This lesson covers giant covalent structures — substances where millions of atoms are all bonded together by covalent bonds in a huge network — as required by the Edexcel GCSE Combined Science specification (1SC0). You need to know the structures and properties of diamond, graphite and silicon dioxide, and be able to explain their properties in terms of their bonding and structure.

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What Is a Giant Covalent Structure?

A giant covalent structure (also called a macromolecular structure) is a substance where all the atoms are linked by strong covalent bonds in a continuous network extending in all directions. There are no individual molecules — the entire structure is one giant lattice of atoms.

Examples include:

• Diamond (a form of carbon)
• Graphite (another form of carbon)
• Silicon dioxide (SiO₂, found in sand and quartz)

Exam Tip: The key difference between giant covalent structures and simple molecules is that giant covalent structures have no weak intermolecular forces to overcome — you must break strong covalent bonds to melt them. This is why they have very high melting points.

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Diamond