Explanation

Rutherford's gold-foil alpha-scattering experiment (the Geiger-Marsden experiment, 1909) showed that while most alpha particles passed straight through, a few were deflected at large angles, proving that the atom's positive charge is concentrated in a tiny, dense nucleus. The neutron, electron and proton were discovered through other experiments. The experiment was performed by Geiger and Marsden in 1909 under Rutherford's direction.