MiniResearch

ELECTRON- In 1897, Sir J. J. Thomas, an English physicist, measured the deflection of cathode-ray particles in magnetic and electrical fields. As a result he found the ratio of the charge, e, to the mass, m, of the cathode-ray particles. He found e/m identical to those particles irrespective of the metal the electrodes were made of or the kind of gas in the tube. In 1909, RA Millikan, an American scientist, measured that charge. All electrons are found to be identical no matter their source or the method of liberating them from matter. From the values of e/m, and e, the mass of an electron was calculated to be .00055 amu. PROTON- Eugeen Goldstein used a Crookes tube with holes in the cathode, and observed that another kind of ray was emitted from the anode and passed through the holes. He discovered this in 1886. In 1889, William Wien showed these rays to be positively charged. The ratio of charge to mass was smaller than electrons, but varied in different gasses. This meant that either charge varied, mass varied or both varied. Both vary. Charge is equal to an electron, but opposite in sign. Mass was smaller when used as a gas. From the values of e/m for positive particles, m was calculated to be 1.0073 amu. This became known as a proton. NEUTRON- In 1932, James Chadwick detected the third of the basic parts of an atom. He showed that uncharged particles, or neutrons, are emitted when atoms of other elements are bombarded with high-velocity helium atoms with all electrons remored, or an alpha particle. Neutrons were determined to have a mass of 1.0087 amu. They are unstable outside of an atom and slowly degenerate to form protons and electrons.