# Explain why the bond angle in sulfur dioxide (SO₂) is approximately 119°, which is less than the bond angle of 120° found in a molecule with an ideal trigonal planar arrangement.

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

> Sulfur dioxide (SO₂) is a bent molecule with a bond angle of approximately 119°.

## Mark scheme (4 marks)

1. The central sulfur atom has three electron domains (two bonding domains and one lone pair), giving a trigonal planar electron domain geometry.
2. The lone pair on sulfur repels the bonding pairs more strongly than bonding pair–bonding pair repulsion.
3. This greater repulsion from the lone pair compresses / pushes the two bonding pairs closer together.
4. The molecular shape of SO₂ is bent / V-shaped (not trigonal planar) because one of the three electron domains is a lone pair and does not contribute to the molecular geometry.

## Key terms

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

## 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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