# Chlorine has two naturally occurring isotopes: chlorine-35 and chlorine-37. Explain what is meant by the term isotope and describe how these two isotopes of chlorine are similar to, and different from, each other in terms of their subatomic particles.

> Eduqas GCSE Chemistry — 2.1 Bonding, structure and properties · Explain · 4 marks

## Mark scheme (4 marks)

1. Isotopes are atoms of the same element with the same number of protons but a different number of neutrons.
2. Both isotopes have the same number of protons (17 protons).
3. Both isotopes have the same number of electrons (17 electrons).
4. The two isotopes have different numbers of neutrons (chlorine-35 has 18 neutrons; chlorine-37 has 20 neutrons).

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/chlorine-has-two-naturally-occurring-isotopes-cd00e01a) · Published by Druglandscape Ltd.