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.
Single-atom transistor Single-atom transistor A single-atom transistor is a device that can open and close an electrical circuit by the controlled and reversible repositioning of one single atom. The single-atom transistor was invented and first demonstrated in 2004 by Prof. Thomas Schimmel and his team of scientists at the Karlsruhe Institute of Technology (former University of Karlsruhe). By means of a small electrical voltage applied to a control electrode, the so-called "gate electrode", a single silver atom is reversibly moved in and out of a tiny junction, in this way closing and opening an electrical contact. Therefore, the single-atom transistor works as