Buckminsterfullerene (C₆₀) is a fullerene used in medical drug delivery systems. Explain why C₆₀ has a low melting point and does not conduct electricity, despite being made entirely of carbon atoms joined by covalent bonds.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Buckminsterfullerene (C₆₀) is a molecule made of 60 carbon atoms arranged in hexagonal and pentagonal rings to form a hollow sphere. It is a solid at room temperature but melts at a relatively low temperature compared to other carbon structures.
Model answer (5 marks)
C₆₀ is a discrete molecule, not a continuous covalent network, so the solid consists of individual C₆₀ units. The molecules are held together only by weak van der Waals forces, which require little energy to break; hence the melting point is low. Each C₆₀ molecule has only σ‑bonds; there are no π‑systems that could delocalise electrons. Without delocalised, mobile electrons, the material cannot carry charge, so it is an electrical insulator.
Examiner tips
- Mention that C₆₀ is a molecular solid, not a network solid.
- Explain that weak van der Waals forces give a low melting point.
- State that C₆₀ has only σ‑bonds, no delocalised electrons, so it does not conduct.
Common mistakes
- Confusing the lack of conductivity with a lack of covalent bonds; all carbon is covalently bonded but not delocalised.
- Forgetting to mention the discrete molecular nature of C₆₀.
- Over‑explaining the structure (e.g., describing the icosahedral symmetry) instead of focusing on the key points.
Mark scheme (5 marks)
- C₆₀ exists as simple molecules (not a giant covalent structure)
- There are intermolecular forces between the C₆₀ molecules
- The intermolecular forces are weak, so little energy is needed to overcome them
- There are no delocalised electrons (free to move) in C₆₀
- Without delocalised (free/mobile) electrons, charge cannot be carried so C₆₀ does not conduct electricity
Key terms in this question
Related
- All OCR A-Level Chemistry A (H432) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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