J. J. Thompson's atomic theory described the inner structure of atoms. According to Encyclopedia Brittanica, the Thompson atomic theory stated that atoms are uniform spheres of positively charged matter with electrons embedded. The theory was proposed around 1900 by Lord Kelvin and was heavily supported by Sir Joseph John Thompson.
In 1897, Thompson discovered the electron, which is a negatively charged part of an atom. The Thompson atomic model was also known as the plum pudding model. Thompson's theory was abandoned in 1911 on theoretical and experimental grounds in favor of the Rutherford atomic model, which proved that Thompson's theory was incorrect. Rutherford's model determined that an atom consisted of a small, dense and positively charged nucleus in the center of the atom with negatively charged electrons surrounding it.