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Graphene and carbon allotropes: structure and properties

Bonding, structure and the properties of matter • Structure and bonding of carbon

Key concepts

What you'll likely be quizzed about

  • Each carbon atom in graphene is sp2 hybridised, producing three coplanar sigma bonds that form a robust hexagonal lattice.
  • The unhybridised p-orbital on each carbon overlaps sideways with neighbours, generating a system of delocalised pi electrons that extends over the entire sheet.
  • The sheet is one atom thick, producing a two-dimensional network with equal bond lengths and bond angles close to 120 degrees.
  • Delocalised electrons enhance charge mobility, while strong sigma bonds between carbon atoms confer high tensile strength and stability.

Flashcards

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Impermeability of graphene to gases

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Dense hexagonal covalent bonding leaves no continuous channel, preventing gas molecules from passing through.

Key notes

Important points to keep in mind

Graphene is one atom thick and forms a two-dimensional hexagonal lattice.

Each carbon in graphene is sp2 hybridised and contributes one delocalised electron.

Delocalised electrons cause in-plane electrical conductivity and equal bond lengths.

Strong sigma bonds in the lattice cause very high tensile strength and thermal conductivity.

Graphene diagrams show flat hexagonal meshes; fullerenes show closed cages with pentagons and hexagons.

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