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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 ....

Middle of Essay
.... 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 ....