Atom of Ernest Rutherford, bombarded a metal foil with alpha particles to observe how they scattered. They expected all the alpha particles to pass straight through with little deflection, because Thomson's model said that the charges in the atom are so diffuse that their electric fields could not affect the alpha particles much. However, Geiger and Marsden spotted alpha particles being deflected by angles greater than 90°, which was supposed to be impossible according to Thomson's model. To explain this, Rutherford proposed that the positive charge of the atom is concentrated in a tiny nucleus at the center of the atom.
A Is for Atom tighter editing, new music and a focus on nuclear power as opposed to nuclear bombs. A narrator is relating what is an atom and how atomic energy can be harnessed by man to produce "limitless" energy. Dr. Atom (a caricature with an atom for a head) then explains the similarities between the solar system and atomic structure. He then goes on to relate how the atom is made up of protons, neutrons, and electrons. After this, the narrator explains how there are more than 90 elements with many possible isotopes for each. The history of atomic energy is then overviewed