The nucleus of the atom was discovered in 1911 by Ernest Rutherford. Through his research, Rutherford figured out that the positive charge of an atom is confined to a tiny but wide region at the center of the atom, rather than it being spread out evenly like Thomson's “plum pudding” model of the atom. To be more specific, after Thomson's experiments with the gold foil he concluded that all of the positive charge and basically all of the mass of the atom are all concentrated in one small area, the center of the atom. And that the rest of the atom is mostly empty space. Rutherford called the center of the atom the nucleus. He figured out that the nucleus contains positively charged particles, which he named protons. Rutherford also predicted the existence of neutral nuclear particles called neutrons, but he failed to find them. However, his student James Chadwick discovered them several years later.
