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Democritus
He was an influential pre-Socratic philosopher and pupil of Leucippus, who formulated an atomic theory for the cosmos. He was boring in 460 BC and died in 370 BC.His exact contributions are difficult to disentangle from his mentor Leucippus, as they are often mentioned together in texts. -
John Dalton
John Dalton was a Chemist, Scientist, and Meteorologist. He was born in 1766 and died in 1844. Dalton's contribution was there was more atoms inside the molecule. -
Joesph John Thompson
Thomson discovered the electron in the year 1897. His work put forward a new theory, that atoms were made up of small particles. Thus he discovered the electron. He proved his theory using the cathodode ray tube. -
Ernest Rutherford
Rutherford was born in 1871 and died in 1937. He discovered alpa and beta rays, set forth the laws of radioactive decay, and identified alpa particles as helium nuclei. most important, he postulated the nuclear structure of the atom. -
Niels Henrik David Bohr
Bohr was born in 1885 and died in 1962. In 1913, Neils Bohr proposed a theory for the Hydrogen atom based on Quantu, theory that engery is transfered only in certain well defines quantities.