The electron was discovered by the British physicist Sir Joseph John "J. J." Thomson in 1897. He identified the electron as a negatively charged subatomic particle through his experiments with cathode rays, demonstrating that these rays were composed of particles much smaller than atoms, later called electrons. Thomson's work fundamentally changed the understanding of the atom, showing it was not indivisible but contained smaller constituents. He estimated the charge-to-mass ratio of the electron and is credited as the discoverer of this fundamental particle.
