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406
Democritus
406 BC - 370 BC
ANcient Greek philosopher who formulated an atomic theory for cosmos. Their hypothesis on atoms is remarkably similar to modern science's understanding of atomic structure, and avoided many of the errors of their contemporaries. -
John Dalton
Also, in 1803, John Dalton created the law of multiple proportions that states that when two elements can combine to form more than one compound the amounts of one of them that combines with a fixed amount of the other will exhibit a simple multiple relation. -
J J Thomson
In 1897 in Cambridge, J J Thomson experimented on cathode rays. In Britain, physicists had argued these rays were particles, but German physicists disagreed, thinking they were a type of electromagnetic radiation. Thomson showed that cathode rays were particles with a negative electric charge and much smaller than an atom. He also thought all atoms contained them. These particles were later named electrons. -
Robert Millikan
Millikan discovered the mass and charge of the electron. He used the Oil Drop Experiment to determine this. -
James Chadwick
Chadwick discovers the neutron 1932. -
Antoine Lavoisier
He named both oxygen (1778) and hydrogen (1783) and helped construct the metric system, put together the first extensive list of elements, and helped to reform chemical nomenclature.
