Ernest Rutherford's main contribution to the study of atomic structure was the discovery of the atomic nucleus. He conducted the famous gold foil experiment, in which he bombarded a thin gold foil with alpha particles. Based on the observation that most of the alpha particles passed straight through the foil, but a small fraction were deflected at large angles, Rutherford deduced that atoms have a tiny, dense, positively charged nucleus at their center, surrounded by a cloud of negatively charged electrons. This overturned the earlier model of J.J. Thomson, who proposed the "plum pudding" model where positive charge was distributed evenly throughout the atom. Rutherford's discovery led to the development of the modern model of the atom and laid the foundation for our understanding of nuclear physics.
