# Ammonia (NH₃) is a covalently bonded molecule with a non-linear, trigonal pyramidal shape. Explain why ammonia is described as covalently bonded and explain why it has a trigonal pyramidal shape rather than a flat, triangular shape.

> Edexcel A-Level Chemistry (9CH0) — 2.2 Covalent bonding and shapes · Explain · 5 marks

> Ammonia has the molecular formula NH₃. Its central nitrogen atom has five electrons in its outer shell.

## Mark scheme (5 marks)

1. Covalent bonding involves the sharing of a pair of electrons between two atoms
2. Each hydrogen atom shares one pair of electrons with the nitrogen atom, forming three covalent bonds
3. The nitrogen atom has one lone pair of electrons (as well as three bonding pairs)
4. The lone pair repels the bonding pairs more strongly than the bonding pairs repel each other
5. This greater repulsion pushes the three N–H bonds below a flat plane, giving a trigonal pyramidal shape (rather than a flat triangular/trigonal planar shape)

## Key terms

- [trigonal pyramidal](https://www.gradenine.co.uk/glossary/trigonal-pyramidal)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/ammonia-nh-is-a-covalently-bonded-001ee9ca) · Published by Druglandscape Ltd.