# Boron has two naturally occurring isotopes, boron-10 and boron-11. The relative atomic mass of boron is 10.8. Explain what is meant by the term 'relative atomic mass' and use this information about boron to explain why its relative atomic mass is closer to 11 than to 10.

> Eduqas GCSE Chemistry — 2.4 Chemical analysis · Explain · 4 marks

## Mark scheme (4 marks)

1. Relative atomic mass is an average value that takes account of the abundance of the isotopes of the element
2. Relative atomic mass is the average mass of an atom of an element compared to 1/12th the mass of a carbon-12 atom
3. Boron-11 must be the more abundant isotope (present in greater proportion / higher percentage)
4. Because boron-11 is more abundant, it has a greater influence on the average, pulling the relative atomic mass closer to 11

## Key terms

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

## Related

- [Revision notes for Eduqas GCSE Chemistry](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/boron-has-two-naturally-occurring-isotopes-19d02f17) · Published by Druglandscape Ltd.