The electrons are distributed around the nucleus and occupy most of the volume of the atom. In the nuclear atom, the protons and neutrons, which comprise nearly all of the mass of the atom, are located in the nucleus at the center of the atom. AND if they already knew that the electron was small and negative, then the atom must have a small positive nucleus with the electrons around them. Rutherfords atomic model became known as the nuclear model. (c) In the cathode ray, the beam (shown in yellow) comes from the cathode and is accelerated past the anode toward a fluorescent scale at the end of the tube. (b) This is an early cathode ray tube, invented in 1897 by Ferdinand Braun. If the positive alpha particles mostly passed through the foil, but some bounced back. Thomson produced a visible beam in a cathode ray tube.
1 Many of the theories of this earlier period were speculative suggestions with little or no foundation in experiment. The concept that matter is composed of discrete particles is an ancient idea, but gained scientific credence in the 18th and 19th centuries when scientists found it could explain the behaviors of gases and how chemical elements reacted with each other. But although rational atomic theory, in the sense of a scientific theory dealing with the internal structure of the atom, dates from the beginning of the twentieth century, ideas of complex atoms and their structure can be found much earlier. How could that be if the plumb pudding model was correct? Rutherford's experiment prompted a change in the atomic model. Atomic theory is the scientific theory that matter is composed of particles called atoms. Rutherford found that most of them went right through the foil.
If you shoot these positive alpha particles at this positive pudding atom, they should mostly bounce off, right? Well, that is not what happened. He shot some alpha particles (which are really just the nucleus of a helium atom) at some really thin gold foil. Ernest Rutherford said one day "hey, I think I will shoot some stuff at atoms." I am sure his wife said "oh, Ernie" (she probably called him Ernie) "if it makes you happy to play with your little physics stuff, go ahead.