Chadwick's experiments showed the existence of neutrons in an atom.
This led to an understanding of isotopes.
Define the term 'isotopes'.
Refer to subatomic particles in your answer.

Isotopes are defined as atoms that have the same number of protons but a different number of neutrons. - **Same number of protons:** The number of protons (the atomic number) determines which element an atom is. Since isotopes are atoms of the same element, they must have the same number of protons. - **Different number of neutrons:** The variation in the number of neutrons leads to a different mass number for each isotope, but it does not change the chemical properties, which are determined by the electron configuration (and thus the number of protons). For example, Carbon-12 has 6 protons and 6 neutrons, while Carbon-14 has 6 protons and 8 neutrons.