What scientific contribution did Thomson make to atomic theory?

Thomson's pivotal contribution to atomic theory was the identification of the electron, which fundamentally changed our understanding of atomic structure. In 1897, through experiments with cathode rays, Thomson demonstrated that these rays were composed of negatively charged particles much smaller than atoms, which he called "corpuscles," later known as electrons. This discovery provided the first evidence of subatomic particles and suggested that atoms were not indivisible as previously thought, but rather composed of smaller elements.

Thomson's work led to the development of the "plum pudding model," where electrons were embedded within a 'soup' of positive charge, suggesting a new way to visualize atomic structure. This was significant because it initiated a shift away from the idea of indivisible atoms toward a more complex understanding of matter, laying the groundwork for future atomic models.