# Iron has atomic number 26. An atom of the most common isotope of iron has a mass number of 56. State the number of protons, neutrons and electrons in one atom of this isotope of iron. Then state what is meant by the term isotope.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 1.2 Atoms · State · 4 marks

## Mark scheme (4 marks)

1. Number of protons = 26
2. Number of neutrons = 30
3. Number of electrons = 26
4. Isotopes are atoms of the same element with the same number of protons but a different number of neutrons

## Key terms

- [atomic number](https://www.gradenine.co.uk/glossary/atomic-number)
- [mass number](https://www.gradenine.co.uk/glossary/mass-number)
- [isotope](https://www.gradenine.co.uk/glossary/isotope)
- [proton](https://www.gradenine.co.uk/glossary/proton)
- [neutron](https://www.gradenine.co.uk/glossary/neutron)
- [electron](https://www.gradenine.co.uk/glossary/electron)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "State" 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/iron-has-atomic-number-26-an-34ec6a19) · Published by Druglandscape Ltd.