# 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 the information given to explain why the relative atomic mass of boron is closer to 11 than to 10.

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

## Mark scheme (5 marks)

1. Relative atomic mass is the average mass of an atom of an element compared to 1/12th the mass of an atom of carbon-12
2. Relative atomic mass takes account of the abundance (proportion) of each isotope
3. Boron-11 must be more abundant than boron-10
4. Because boron-11 is more abundant, the average is pulled closer to 11 than to 10

## 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 A-Level 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-8e81084b) · Published by Druglandscape Ltd.