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Carbon Structures

Chemistry: AQA A Level, topic 1.3.3

Diamond

Diamond is an allotrope (form) of carbon. Diamond has the following properties:

Covalent bonds

Covalent bonds

  • Each carbon atom in diamond is bonded to four other carbon atoms by strong covalent bonds.
  • This creates a giant covalent structure.
Hard

Hard

  • There are lots of strong covalent bonds in diamond. This makes it very hard.
  • Because diamond is hard, it is used as a cutting tool to cut other materials.
Does NOT conduct electricity

Does NOT conduct electricity

  • Diamond does NOT conduct electricity because there are no delocalised electrons in the diamond structure.
High melting point

High melting point

  • A lot of energy is needed to break strong covalent bonds.
  • Diamond has lots of strong covalent bonds. This means that it has a high melting point.
Thermal conductivity

Thermal conductivity

  • Diamond has a very rigid structure.
  • This means that vibrations can easily carry heat throughout the structure.
  • Diamond is an excellent thermal conductor.

Graphite

Graphite is an allotrope (form) of carbon. Graphite has the following properties:

Covalent bonds

Covalent bonds

  • Each carbon atom in graphite is bonded to 3 other carbon atoms by strong covalent bonds.
  • This creates a giant covalent structure.
Strong covalent bonds

Strong covalent bonds

  • Due to the strong covalent bonds within the sheets, graphite:
  • Has a high melting point.
  • Is insoluble in solvents.
Soft

Soft

  • The carbon atoms form layers of hexagonal (6-sided) rings, with each layer held together by weak intermolecular forces.
  • The layers can slide over one another easily, so graphite is very soft.
  • This makes it useful as a lubricant and as pencil ‘lead’.
Conducts electricity

Conducts electricity

  • Each carbon atom forms 3 covalent bonds.
  • 1 electron from every carbon atom in graphite is delocalised.
  • This electron can move freely, so graphite can conduct electricity.

Test yourself on Carbon Structures

  • Which of the following best describes diamonds?

  • Which of the following are properties of diamond?

  • How many other carbon atoms is each carbon atom in diamond bonded to?

  • Which of the following are properties of graphite?

  • Why does graphite conduct electricity?

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