Giant covalent substances

In a nutshell

A giant covalent substance contains strong covalent bonding between its atoms. Diamond, graphite and graphene are all examples of giant covalent substances made from carbon.

Giant covalent structures

Giant covalent structures contain strong covalent bonds between atoms. They contain giant lattice structures.

General properties of giant covalent substances

Very high melting and boiling points, as high amounts of energy is needed to break the strong covalent bonds.
Giant covalent structures do not contain any charged or free particles, so they do not conduct electricity.
Not soluble in water.

Note: Sometimes there are exceptions to the conductivity rule, graphite and graphene are giant covalent substances that will conduct electricity.

Carbon giant covalent substances

SUBSTANCE	STRUCTURE	MELTING/BOILING POINTS	CONDUCTIVITY
Diamond	Four covalent bonds per carbon atom. Regular and rigid structure which makes diamond hard.	High (due to strong covalent bonds).	No free particles. Does not conduct electricity.
Graphite	Three covalent bonds per carbon atom. Hexagon sheets of carbon atoms. No covalent bonds between the hexagon sheets, so the layers are held weakly and graphite is soft.	High (due to strong covalent bonds).	One delocalised electron per carbon atom that will carry an electrical charge. Will conduct electricity.
Graphene	One layer of graphite (three covalent bonds per carbon atom). One sheet of carbon hexagons. One layer thick, so two-dimensional.	High (due to strong covalent bonds).	One delocalised electron per carbon atom that will carry an electrical charge (as made from graphite). Will conduct electricity.

Fullerenes

Fullerenes are made from ringed carbon molecules shaped in tubes.

Their tubed structure has important uses:

To trap other substances, this is useful when delivering drugs.
High surface area makes them useful as catalysts.

Nanotubes are fullerenes made from small cylinders of graphene. The high tensile strength of fullerenes makes them useful to strengthen materials without adding large amounts of weights. This makes them useful in sporting equipment.

Structures of each giant covalent substance

substance	structure	description
Diamond		Regular structure, each carbon with four bonds.
Graphite		Layers of hexagon shaped carbon atoms held together weakly.
Graphene		Single layer of graphite.
Fullerenes		Tube of carbon molecules.