Giant covalent structures

A small number of covalent substances form giant structures instead of small molecules. In these structures, the atoms are bonded to each other with covalent bonds.

Examples

Silicon dioxide, also called silica, is the main compound found in sand. It is an example of a substance with a giant covalent structure. It contains many silicon and oxygen atoms.

All the atoms in its structure are linked to each other by strong covalent bonds. The atoms are joined to each other in a regular arrangement, forming a giant covalent structure. There is no set number of atoms joined together in this type of structure.

Diamond is another example of a giant covalent structure. Diamond is made up of carbon atoms - it is a form of carbon.

Covalent structure of silicaSilica has a giant covalent structure containing silicon atoms (grey) and oxygen atoms (red)

High melting points and boiling points

Substances with giant covalent structures are solids at room temperature. They have very high melting points and boiling points. This is because large amounts of energy are needed to overcome their strong covalent bonds to make them melt or boil.

Conduction of electricity

Most substances with giant covalent structures have no charged particles that are free to move. This means that most cannot conduct electricity. Graphite, a form of carbon which can conduct electricity, is an exception.

Question

State three properties that are typical of substances with giant covalent structures.

They have high boiling points, high melting points and they cannot conduct electricity.

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