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John Dalton
He studied color-blindness. He was the first person to discover that all matter was built up of atom and a chemical reaction is a rearrangement of atoms -
Bohr
Bohr investigated atomic structure and radiation -
Rutherford
Shot a beam of alpha rays at a sheet of gold foil. Most of the particles went though the sheet but some bounced back. -
Thomson
He had to make alot of experiments to find out his theory. He investigated cathode rays and he said that the rays were made up of electrons and they were streams of particles smaller tham atoms