Ernest Rutherford gets credit for the discovery of the proton. While conducting the first experiment in splitting the atom between nitrogen and alpha particles, he discovered what had been hypothesized for many years before: the proton.
Ernest Rutherford is considered to be the father of nuclear physics. Many of his discoveries about radioactivity and the nature of atoms propelled the world into the nuclear age, as well as a better understanding about the makeup of the elements. His observation that the atoms of extremely heavy elements have a tendency to decay has changed the world forever, as it brought on an accurate way to judge the age of objects via carbon dating.