Discovery of the Atom’s Electron

• Thomson’s charge to mass experiment investigated the effect on a cathode ray when placing an electric field around a tube.
• Charged matter is attracted to an electric field.
• Light’s path is not deflected by an electric field.
• Cathode rays are made of tiny particles.
• These particles had a negative charge because the beam always deflected toward the (+) plate.
• The amount of deflection was related to the charge and mass of the particles.
• The charge–mass ratio of these particles was (−)1.76 × 108 C/g.