Students should be able to explain the properties of graphene in terms of…

The idea

Graphene is a single layer of graphite, one atom thick, in which each carbon atom is covalently bonded to three others in a flat hexagonal lattice. The fourth outer electron per atom is delocalised across the layer, so graphene conducts electricity and thermal energy well. Because the layer is only one atom thick, it is transparent and extremely light. Graphene has a very high melting point and is insoluble in water because of the strong covalent bonds within the layer, which require a large amount of energy to break.

For example: Graphene can be used in touchscreens because it conducts while remaining transparent, and in composite materials where strength with low mass matters.

What earns the marks

• Graphene is a single layer of graphite that is one carbon atom thick.
• Each carbon atom forms three covalent bonds to other carbon atoms, giving a flat hexagonal lattice.
• Each carbon atom contributes one delocalised electron, so graphene conducts electricity and thermal energy.
• The strong covalent bonds within the layer give graphene a very high melting point and great strength.
• The one-atom-thick layer makes graphene transparent and very light, which suits uses such as touchscreens and composites.
• Properties must be linked to structure and bonding, not simply listed.

Common mistakes and how to put them right

• Saying graphene is a molecule of carbon.

  Put it right by describing graphene as a giant covalent structure or single layer of graphite.

• Stating that graphene has a low melting point due to weak intermolecular forces.

  Put it right by noting that a single graphene sheet has strong covalent bonds throughout, requiring substantial energy to break.

• Claiming graphene does not conduct because carbon is a non-metal.

  Put it right by explaining that delocalised electrons from the fourth outer electron of each carbon atom carry charge.

Exam tips

• Always name the bond type and the number of bonds per carbon atom when explaining a property.
• Link each property to a specific use, such as transparency plus conductivity for touchscreens.
• Use comparative language such as 'one atom thick' and 'very high melting point' to show scale and strength.