Before Rutherford's discovery, the accepted atomic model was J. J Thompson's Plum Pudding Model. According to J.J Thompson, the atom is composed of negatively charged particles. They were then called 'corpuscles', but now known to be electrons. Outside of this atom, surrounds a cloud of positively charged electrons to balance out the charge of electrons, which makes the atom neutral. The 'plum' were the electrons, whereas the 'pudding' were the protons.
Through Rutherford's gold foil experiment, he disproved J.J Thompson's theory. Rutherford was very interested in studying the behavior of x-rays, which was then recently discovered by Curie. When he shot a beam of alpha particles (particles with 2 neutrons and 2 protons, or the Helium atom) toward the gold foil, the particles were deflected by a slight angle. He then theorized that these deflections were due to the existence of a dense nucleus inside the atom.
Following Rutherford's discovery of the nucleus, Niels Bohr theorized the planetary model of the atomic structure. According to him, the atom is like a solar system wherein the Sun is the nucleus and the planets are the electrons orbiting around it. The electrons and protons move this way because they are influenced by an electric force due to the difference of their charges.
