Abstract: This chapter focuses on Lord Kelvin's works on atoms and molecules. He published his first paper on the subject in 1861 and his last in 1907. His first foray into atoms and molecules was to estimate their size. His investigation of molecular models, his opposition to kinetic theory, his introduction of gyrostatic molecules, studies on electrons and radioactivity, and lectures at Johns Hopkins University are discussed.

Keywords: Lord Kelvin, atoms, molecules, physicists, kenetic theory,