Isotopes 1
Physics: Edexcel IGCSE, topic 7.1.8
Isotopes
Atoms of the same element always have the same number of protons (or have the same atomic number). However, atoms of the same element can have different numbers of neutrons. We call these different isotopes. Hydrogen has 3 different isotopes:
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Protium
- Protium is a hydrogen atom with 1 proton and 0 neutrons.
- 99.98% of hydrogen atoms are protium.
- It is used in hydrogen fuel cells and the production of plastics.
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Deuterium
- Deuterium is a hydrogen atom with 1 proton and 1 neutron.
- Around 0.02% of hydrogen atoms are deuterium.
- It is used in nuclear fusion.

Tritium
- Tritium is a hydrogen atom with 1 proton and 2 neutrons.
- It is very rare.
- It is used in thermonuclear fusion weapons.
Test yourself on Isotopes 1
Isotopes of hydrogen
Protium contains 0 neutrons and tritium contains 2 neutrons. How many more neutrons does tritium have than protium?