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Period: 400 to 405
Democritus
Domocritus suggests that matter cannot be infinatly divided. He suggested that matter is made of atomos, and said that atomos cannot be created destroied or divided. Events actually took place between 460 and 370 BC. -
Period: 420 to 425
Aristotle
Aristotle completely denied the theory of atomos from 380-320. This probably set back atomic theory. -
Period: to
John Dalton
Dalton was the first to establish modern Atomic theory. He revised Democritus' teachings, and renamed the atomos to atom. -
Period: to
Sir William Cooke
Used Cathode rays to investigate the behavior of electricity in the absense of matter. Led to the invention of the television. -
Period: to
J.J. Thomsom
Thomson created a ratio of a particles charge to mass. DIscovered the electron. Thomson proposed the plum pudding model. This model said that an atoms postive charge was uniformly distributed and the negtive charge was dispersed at random throughout the atom, much like plums in plum pudding. -
Period: to
Robert Millikan
Millikan used an oil drop apparatus to determine the charge of an electron. He used the charge- mass ratio to find the mass of an electron. -
Period: to
Earnest Rutherford
Rutherford used the gold foil experiment to propose that the plum pudding was wrong. He said that atoms were mostly just empty space for the electrons to move around in and the majortiy of the mass was contained in a tiny extremely dense point called the nucleus. Rutherford also introduced the proton, a positivly charged particle. -
Chadwick
In 1935 Chadwick won the nobel prize for his discovery of the neutron, a particle with no charge.