# Explain why graphene is an electrical conductor, whilst poly(ethene) is an electrical insulator, despite both materials consisting predominantly of carbon and hydrogen atoms.

> IB DP Chemistry Standard Level (2023 syllabus) — S2.4 From models to materials · Explain · 4 marks

> Graphene is a single layer of carbon atoms arranged in a planar hexagonal lattice. Poly(ethene) is a polymer formed by addition polymerisation of ethene monomers.

## Mark scheme (4 marks)

1. In graphene, each carbon atom forms three sigma bonds leaving one electron in an unhybridised p orbital (or: each carbon has a non-bonding/delocalised electron).
2. These p electrons overlap across the entire graphene layer to form a delocalised system of electrons that can move freely and carry charge.
3. In poly(ethene), all four valence electrons of each carbon are used in sigma (single covalent) bonds to hydrogen or adjacent carbon atoms.
4. Because there are no delocalised electrons in poly(ethene), no charge carriers are available and the material cannot conduct electricity.

## Key terms

- [electrical conductor](https://www.gradenine.co.uk/glossary/electrical-conductor)
- [insulator](https://www.gradenine.co.uk/glossary/insulator)
- [poly(ethene)](https://www.gradenine.co.uk/glossary/poly-ethene)
- [graphene](https://www.gradenine.co.uk/glossary/graphene)

## Related

- [Revision notes for IB DP Chemistry Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-graphene-is-an-electrical-6075ee26) · Published by Druglandscape Ltd.