How did JJ. Thomson contribute to the atomic theory? JJ. Thompson contributed to the atomic theory by discovering the electron. He experimenting with a cathode ray, he demonstrated that cathode rays were negatively charged. Electrons play a major role in chemical bonds which result in a molecule or a compound formation. This is important to atomic theory because this discovery upended the prevailing theory that the atom was the smallest fundamental unit.
Thomson was pushing his powerful mathematical mind towards a deeper understanding of matter. At the time atoms were still regarded as indivisible. Thomson allowed his cathode rays to travel through air rather than the usual vacuum and was surprised at how far they could travel before they were
