The Thomson model, proposed by physicist J.J. Thomson in 1897, describes the structure of an atom as a sphere of positive charge with negatively charged electrons embedded within it, similar to a "plum pudding." This model was developed after Thomson discovered the electron, suggesting that atoms are not indivisible but contain smaller particles. The Thomson model was significant in the early understanding of atomic structure, but it was later replaced by the Rutherford model in 1911, which introduced the concept of a dense nucleus surrounded by orbiting electrons. Despite its limitations, the Thomson model laid the groundwork for future atomic theories.