Giant covalent structures
3 marks · NormalC60 fullerene, diamond and graphite are all allotropes of carbon. Explain how the structure and bonding in C60 fullerene differs from that in diamond and graphite.
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C60 fullerene has a simple molecular structure made of separate C60 molecules with weak intermolecular forces, while diamond and graphite have giant covalent structures with many atoms joined in a continuous network by strong covalent bonds. In diamond, each carbon atom forms four covalent bonds in a 3D lattice. In graphite, each carbon forms three covalent bonds in layers, with delocalised electrons, but still forms a giant structure. In C60, each carbon atom forms three bonds, but the electrons cannot move between molecules.
Also accept: C60 has simple molecular structure of molecules, not a giant network. Diamond and graphite are networks of carbon atoms bonded covalently throughout, while C60's molecules are held together by weak forces.; C60 is made of many separate molecules (simple structure), while diamond and graphite are made from a continuous, huge covalent network.
Common mistakes: saying C60 is giant structure; missing bonding details
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Marking points
M1 · 1 mark · States C60 has a simple molecular structure made of C60 molecules.
M2 · 1 mark · States diamond and graphite are giant covalent networks.
A1 · 1 mark · Compares bonding: Diamond has four covalent bonds per carbon; graphite three per carbon and delocalised electrons; C60 has three bonds per carbon within a molecule but weak intermolecular forces between molecules.
Worked solution
C60 fullerene is made up of individual C60 molecules held together by weak intermolecular forces. It has a simple molecular structure. Diamond and graphite both have giant covalent structures: diamond forms a 3D lattice where each carbon atom bonds to four others, graphite forms layers with strong bonds in layers and weak forces between the layers. The main difference is that diamond and graphite are continuous networks whereas C60 consists of separate molecules.