# Explain why the bond angle in ammonia (NH₃) is approximately 107°, which is less than the bond angle of 109.5° found in methane (CH₄).

> IB DP Chemistry Standard Level (2023 syllabus) — S2.2 The covalent model · Explain · 4 marks

## Mark scheme (4 marks)

1. Electron pairs (electron domains) arrange themselves to minimise repulsion / VSEPR principle stated
2. NH₃ has three bonding pairs and one lone pair (tetrahedral electron geometry / four electron domains around nitrogen)
3. A lone pair exerts greater repulsion than a bonding pair because it is closer to / more concentrated around the central atom
4. The greater lone pair repulsion pushes the three N–H bonds closer together, reducing the H–N–H bond angle below 109.5° to approximately 107°

## Key terms

- [bond angle](https://www.gradenine.co.uk/glossary/bond-angle)

## 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)
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