J.J. Thomson made groundbreaking contributions to the atomic theory through his discovery of the electron in 1897. His experiments with cathode rays led him to propose that atoms are not indivisible, as previously believed, but instead contain smaller particles. This was a significant shift in scientific thought, suggesting that the atom could be broken down into simpler components.
Thomson’s work involved passing electric currents through gases at low pressure, which resulted in the emission of cathode rays. He observed that these rays could be deflected by electric and magnetic fields, leading him to conclude that they were made up of negatively charged particles. He named these particles ‘corpuscles,’ which we now call electrons.
His discovery laid the foundation for the modern understanding of atomic structure. In 1904, Thomson proposed the ‘plum pudding model’ of the atom, where electrons were embedded within a positively charged ‘soup.’ Although this model was later replaced by the more accurate planetary model proposed by Ernest Rutherford, Thomson’s identification of the electron was a crucial step in the development of atomic theory.
In summary, J.J. Thomson’s identification of the electron as a subatomic particle challenged the notion of the atom as indivisible and led to advancing our understanding of atomic structure.