Isotopes (Edexcel IGCSE Physics (Modular))

Isotopes

• For a particular element, the number of protons is always the same, but the number of neutrons can be different

  • This is because the number of protons determines the element e.g. carbon atoms have 6 protons and iron atoms have 26 protons

• An isotope is defined as:

An atom, or atoms, of the same element that have an equal number of protons but a different number of neutrons

• Each element can have more than one isotope

Isotopes of hydrogen

• Some isotopes are more unstable than others due to the imbalance of protons and neutrons, which means

  • They may be more likely to decay

  • They may be less likely to occur naturally

• For example, about 2 in every 10 000 atoms of hydrogen are the isotope deuterium

  • The isotope tritium is even rarer (about 1 in every billion billion atoms of hydrogen)