Part 1 of Essay
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 ....

Part 2 of Essay
.... 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 r ....