Greek philosopher first to introduce atoms he thought they were invisible. Unable to separate or divide. Other scientist built on his work in the 1800's but they did observations and experiments.
Democritus
John Dahlton
Used data from air pressure and water vapor experiments to devise his atomic theory.
Presented a theory that was difficult to prove because atoms cant be observed directly
J.J Thomson
Used cathode tubes. Determined the particle that produced electric current. Discovered that atoms have charges
Ernest Ruthford
Developed a experiment to test the plum pudding model.