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John Dalton
John Dalton started his experiment in 1803 and finished around 1808. His theory was that the law of conservation of mass and the law of definite proportions could be explained using the idea of atoms. -
JJ Thomson
JJ Thomson started his experiment in 1894 and ended around 1897. His theory was that all atoms contain tiny negatively charged subatomic particles or electrons. He created the plum pudding model that was later disproved but still relevant. -
Ernest Rutherford
He conducted and created several tests to prove that the nucleus of an atom is actually quite small. The experiment that he conducted was called the gold foil experiment. In this experiment he sent alpha particles through gold foil to see if they would go all the way through. He found out that the nucleus is dense, has a positive charge and is small. -
Neils Bohr
He started his experiment in 1913 and went to about 1930. He proposed a theory for the hydrogen atom, based on quantum theory that some physical quantities only take discrete values. Electrons move around a nucleus, with prescribed orbits, and if electrons jump to a lower energy orbit, the difference is sent out as radiation. -
James Chadwick
In 1932 Chadwick made a fundamental discovery in the domain of nuclear science. He proved the existence of neutrons-elementary particles devoid of any electrical charge. He created an atomic model with positively charged protons, neutral neutrons bound together as the atom's of the nucleus.