# Neon has two naturally occurring isotopes, neon-20 and neon-22. Explain what is meant by the term isotope and explain why the relative atomic mass of neon is not a whole number.

> Eduqas A-Level Chemistry — 2.3 Transition metals (A-Level only) · Explain · 5 marks

## Mark scheme (5 marks)

1. Isotopes are atoms of the same element with the same number of protons but a different number of neutrons
2. Neon-20 and neon-22 exist in different proportions / abundances
3. Relative atomic mass is an average value that takes account of the abundance of the isotopes
4. Because the weighted average of the isotope masses is not a whole number, the relative atomic mass is not a whole number

## Key terms

- [isotope](https://www.gradenine.co.uk/glossary/isotope)
- [relative atomic mass](https://www.gradenine.co.uk/glossary/relative-atomic-mass)

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Source: [GradeNine](https://www.gradenine.co.uk/q/neon-has-two-naturally-occurring-isotopes-54508499) · Published by Druglandscape Ltd.