Giant Covalent Structures (Diamond, Graphite, Silicon Dioxide)

This lesson covers giant covalent structures as required by the AQA GCSE Combined Science Trilogy specification (8464), section 4.2.2. You need to know the structures and properties of diamond, graphite and silicon dioxide, and explain why their properties differ from simple molecular substances.

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What Is a Giant Covalent Structure?

A giant covalent structure (also called a macromolecular structure) is a huge network of atoms all joined together by strong covalent bonds. Unlike simple molecular substances, there are no small individual molecules — the entire structure is one continuous network of covalently bonded atoms.

Because all the bonds are strong covalent bonds that extend throughout the whole structure, giant covalent substances have very high melting and boiling points.

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Diamond

Structure

• Diamond is a form of carbon (C).
• Each carbon atom is covalently bonded to 4 other carbon atoms in a tetrahedral arrangement.
• The structure forms a rigid 3D lattice that extends in all directions.
• All outer-shell electrons are involved in bonding — there are no free electrons.