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Isotopes - IGCSE Physics Definition

Reviewed by: Leander Oates

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What are isotopes?

In IGCSE Physics, isotopes are different forms of the same chemical element that have the same number of protons but a different number of neutrons in their nuclei.

Isotopes of the same element have the same atomic number but different mass numbers, giving them slightly different physical properties while maintaining the same chemical properties.

Diagram showing hydrogen isotopes: hydrogen with 1 proton, deuterium with 1 proton and 1 neutron, tritium with 1 proton and 2 neutrons.
Hydrogen has three isotopes, each with a different number of neutrons

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Leander Oates

Reviewer: Leander Oates

Expertise: Senior Physics Content Creator

Leander graduated with First-class honours in Science and Education from Sheffield Hallam University. She won the prestigious Lord Robert Winston Solomon Lipson Prize in recognition of her dedication to science and teaching excellence. After teaching and tutoring both science and maths students, Leander now brings this passion for helping young people reach their potential to her work at SME.

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