Who was jj Thompson and when did he develop his atomic theory?

J.J. Thomson was a British physicist best known for his discovery of the electron in 1897. He developed his atomic theory in the late 19th century, proposing the "plum pudding" model of the atom, which suggested that atoms were composed of a positively charged "soup" with negatively charged electrons embedded within it. His work laid the foundation for modern atomic physics and significantly advanced the understanding of atomic structure.