Methodology
He determined this by bombarding gold foil with alpha particles, and observing the scattering of these particles, a procedure requiring many hours in a darkened room watching for tiny flashes of light as the scattered particles struck a scintillant screen. Rutherford was surprised to observe that most of the particles passed through the foil without any deflection; under the plum pudding model, charge would be distributed thickly in the foil, and very few particles would avoid deflection. This result implied that, on the contrary, most of the apparently solid metal was, in fact, empty space. Even more surprising, a tiny number of the particles underwent larger deflections in their path: some were even bounced back from the foil. Under the plum-pudding model, thus is akin to a sheet of paper to bouncing back bullets.
His findings led Rutherford to the conclusion that the atom is mostly empty space, with most of the atom's mass concentrated in a relatively tiny centre, the nucleus.
The experiment failed to yield any data concerning electrons (which had to be present in order to make the atom electrically neutral). Rutherford did surmise that they would have a very small mass, and that they would be randomly distributed around the nucleus.Conclusions