Atom. By Leo7a11 Nov 30, 1803 Introduction of the atom. Aug 1, 1886 Discovery of the proton. Nov 30, 1897 Discovery of the electron. Nov 30, 1897 Thompson Cathode Ray Discovery Nov 30, 1910 Robert Millikan's Charge of a Electron Aug 1, 1911 The Discovery of the Nucleus Nov 30, 1911 Nucleus Nov 30, 1911 Rutherford's Gold Foil Experiment Discovery Nov 30, 1913 Niels Bohr Nov 30, 1913 Electrons Orbitals Aug 1, 1932 Discovery of the Neutron Aug 1, 1948 Maria Goeppert-mayer