# Explain why carbon nanotubes exhibit exceptionally high tensile strength and are also able to conduct electricity along their length.

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

> Carbon nanotubes (CNTs) are cylindrical allotropes of carbon in which the carbon atoms are arranged in a hexagonal lattice rolled into a seamless tube. They have tensile strengths far exceeding that of steel and can conduct electricity along their axis.

## Mark scheme (4 marks)

1. Each carbon atom forms three sigma (σ) bonds to neighbouring carbon atoms in a trigonal planar / sp² hybridised arrangement, creating a continuous, rigid covalent network along and around the tube.
2. The strong, directional covalent bonds require large amounts of energy to break, accounting for the exceptionally high tensile strength.
3. The fourth valence electron of each carbon atom is not involved in sigma bonding and occupies a p orbital perpendicular to the tube wall, forming a delocalised π system.
4. These delocalised π electrons are mobile along the length of the tube and can carry charge, allowing electrical conduction along the nanotube axis.

## Key terms

- [carbon nanotube](https://www.gradenine.co.uk/glossary/carbon-nanotube)
- [tensile strength](https://www.gradenine.co.uk/glossary/tensile-strength)

## Related

- [Revision notes for IB DP Chemistry Higher 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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-carbon-nanotubes-exhibit-exceptionally-4f857baa) · Published by Druglandscape Ltd.