# Explain why two atoms that are isotopes of the same element have identical chemical properties but different physical properties such as density.

> Eduqas GCSE Physics — 9.1 Nuclear atom and isotopes · Explain · 4 marks

> Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.

## Mark scheme (4 marks)

1. Isotopes have the same number of protons (and electrons), so the same electronic structure
2. Chemical properties depend on the number / arrangement of electrons, so chemical properties are the same
3. Isotopes have different numbers of neutrons, giving different mass numbers
4. Different mass means different physical properties such as density, so physical properties differ

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-two-atoms-that-are-f7aebc22) · Published by Druglandscape Ltd.