empty space
While the great majority of the alpha particles did pass straight through the foil with no deflection, to everyones surprise, some alpha particles were deflected. In fact, some alpha were bounced almost straight backward by the foil. Rutherford, using Coulombs law and Newtons laws found that the results could be explained only if all the positive charge of the atom were concentrated in a tiny, central core, now called the nucleus . Rutherfords model of the atom is therefore, called the nuclear model of the atom. All of the positive charge and essentially all of the mass of the atom are in its nucleus. The atom is 10,000 times as large as the nucleus and is mostly empty space. It was known that electrons are outside the nucleus but how the electrons were arranged in an atom was still a mystery.