- Each carbon atom in graphite is bonded to three others forming layers of hexagons, leaving one free electron per carbon atom
- These free electrons migrate along the layers and are free to move and carry charge, hence graphite can conduct electricity
- The covalent bonds within the layers are very strong, but the layers are attracted to each other by weak intermolecular forces, so the layers can slide over each other making graphite soft and slippery
Diagram showing the structure and bonding arrangement in graphite
- Graphite has the following physical properties:
- It conducts electricity and heat
- It has a very high melting point
- It is soft and slippery and less dense than diamond (2.25 g/cm3)
- Graphite ́s weak intermolecular forces make it a useful material
- It is used in pencils and as an industrial lubricant, in engines and in locks
- It is also used to make inert electrodes for electrolysis, which is particularly important in the extraction of metals such as aluminium
Don’t confuse pencil lead with the metal lead – they have nothing in common. Pencil lead is actually graphite, and historical research suggests that in the past, lead miners sometimes confused the mineral galena (lead sulfide) with graphite; since the two looked similar they termed both minerals ‘lead’.
The word graphite derives from the Latin word ‘grapho’ meaning ‘I write’, so it is a well named mineral!