Question

Scientific experiments showed evidence that the mass of an atom was greater than the total mass of its protons. These experiments led to the discovery of the

nucleus.
neutron.
electron.
proton.

Answer 1

The answer to your question is;
Neutron

Answer 2

Neutron.

Because, the mass of atoms was found to be greater than the mass of protons, scientists believed that there was some other sub atomic particle that added to the mass of protons to give the total mass of atoms.
So the neutron was discovered.

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