J.J. Thomson discovered the electron in 1897. He demonstrated through experiments with cathode rays that these rays were composed of previously unknown negatively charged particles much smaller than atoms, which he originally called "corpuscles" (later called electrons). This discovery proved that atoms were divisible and had smaller components, overturning the then- accepted notion that atoms were indivisible. Thomson also determined the mass- to-charge ratio of the electron and proposed that electrons were present in all matter. This laid the foundation for modern atomic theory and the understanding of chemical bonding. Additionally, Thomson proposed an atomic model known as the "plum pudding model," describing electrons distributed within a positively charged sphere.