Ernest Rutherford's famed Gold Foil Experiment of 1909 demonstrated that atoms were made up of a charged nucleus orbited by electrons. He published his findings in 1911 with a description of what he called the Rutherford model of the atom. While electrons had been described prior to this experiment, Rutherford was the first person to describe the existence of a small, charged atomic nucleus.
Rutherford's Gold Foil Experiment involved the passage and deflection of alpha particles through a thin sheet of gold. The deflection of the alpha particles occurred because the charged nucleus of the gold atoms changed the trajectory of the alpha particles. This observation was inconsistent with the current model of the atom, driving Rutherford's nucleus theory.
Prior to his discovery of the atomic nucleus, Rutherford received the Nobel Prize in Chemistry in 1908 for his discovery of radioactive half-lives and his differentiation between alpha and beta radiation.
In 1917, Rutherford was the first person to successfully split an atom using nitrogen and alpha particles. This reaction led to his discovery of protons, which are contained in the atomic nucleus.
As a mentor, he was instrumental in James Chadwick's discovery of the neutron, a component of the atomic nucleus, in 1932.