Giant Covalent Structures

This lesson covers giant covalent structures, as required by the AQA GCSE Chemistry specification (4.2.2). You need to understand the structures and properties of diamond, graphite, graphene, and fullerenes (including buckminsterfullerene and carbon nanotubes). These substances have very different properties from simple molecular substances because their covalent bonds extend throughout the entire structure.

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What Are Giant Covalent Structures?

A giant covalent structure (also called a macromolecular structure) is a three-dimensional network of atoms connected by strong covalent bonds in all directions. Unlike simple molecules, there are no individual molecules — the entire structure is one giant molecule.

Because all the bonds are strong covalent bonds, a huge amount of energy is needed to break them, giving these substances very high melting and boiling points.

Exam Tip: The key phrase for giant covalent structures is "many strong covalent bonds that require a large amount of energy to break." This directly explains the very high melting points. Always link the property to the bonding.

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Diamond

Diamond is an allotrope of carbon. An allotrope is a different structural form of the same element in the same physical state.

Structure of Diamond