Key Concepts: Giant Covalent Structures and Fullerenes

Giant covalent structures, also known as macromolecules, are substances that consist of many atoms joined together by covalent bonds in a very large and complex network.
Examples of giant covalent structures include diamond, graphite, and silicon dioxide.
Properties of giant covalent structures include a high melting and boiling point due to the many strong covalent bonds that require a great deal of energy to break, as well as their general hardness and rigidity.
Diamond is an example of a giant covalent structure. It is made of carbon atoms and is incredibly hard due to the four covalent bonds joining each atom to its neighbours.
Graphite, also a carbon-based giant covalent structure, has layers which can slide over each other. This layer arrangement means each carbon atom is only bonded to three others, leaving a free electron that can move – allowing graphite to conduct electricity.
Silicon dioxide (or silica), another giant covalent structure, forms the main component of sand. It has a very high melting point and forms a hard, brittle solid.
Fullerenes are molecules of carbon, shaped like tubes or balls. Examples include Buckminsterfullerene (C60) with a spherical shape and nanotubes with a cylindrical form.
Fullerenes can be used to ‘cage’ other molecules, as the spaces within them are large enough to hold these captive. This ‘caging’ has potential uses in targeted drug delivery in the body, in lubricants, and in catalysts.
The special structure of fullerenes gives them unique properties such as the ability to conduct electricity and heat.
Nanotubes, a form of fullerene, are incredibly strong and are good conductors of heat and electricity due to the nature of their carbon-to-carbon bonds. These properties make them useful in nanotechnology, electronics and materials science.
Unlike giant covalent structures, fullerenes have relatively low melting and boiling points due to the weak intermolecular forces between the molecules that need only a small amount of energy to break.