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.

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.

Hope This Helps You!

Ithink that the use of creativity in the sciences entails that one produce something out of nothing or from another thing. with this, i think that the he wrote down his results as four parts of the atomic theory is the manifestation of the  creativity of john dalton.