Answer:
J.J. Thomson
Explanation:
J. J. Thomson. discovered in 1897 that all atoms has at least one electron, at least one negatively charged subatomic particle.
Thomson discovered this based on experiments on the properties of cathode rays. To verify the properties of the particles, Thomson placed the cathode ray tube between two plates with opposite charges, and verified that the beam deviated, moving away from the negatively charged plate and approaching to the positively charged plate. From this fact he concluded that the beam was composed of negatively charged particles.
