In 1897, Thomson showed that cathode rays were composed of a previously unknown negatively charged particle, and thus he is credited with the discovery and identification of the electron; and, in a broader sense, with the discovery of the first subatomic particle.
In 1897, Thomson showed that cathode rays were composed of previously unknown negatively charged particles, with "bodies much smaller than atoms", and a very large value for their charge-to-mass ratio. Thus he is credited with the discovery and identification of the electron; and with the discovery of the first subatomic particle.