Answer :
Final answer:
James Chadwick discovered the neutron, a neutral subatomic particle with mass similar to protons, which explains isotopes.
Explanation:
James Chadwick discovered the neutron, a neutral subatomic particle with mass similar to protons, in 1932. Neutrons, along with protons, constitute the nucleus of an atom. The existence of neutrons explained the concept of isotopes, which are atoms of the same element with different masses due to varying numbers of neutrons.
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