Atom bombardment ejects what appeared to be hydrogen nuclei. By 1920 he had accepted that the hydrogen nucleus is a distinct particle within the atom and named it proton. Neutrons have no electrical charge and have a free mass of 1,839 times the mass of the electron, or , the heaviest of the three constituent particles, but it can be reduced by the nuclear binding energy. Neutrons and protons (collectively known as nucleons) have comparable dimensions—on the order of —although the 'surface' of these particles is not sharply defined. The neutron was discovered in 1932 by the English physicist James Chadwick.
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