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  460 BC-370 BC
Believed matter was made up of atoms which he said where physically indivisble, has space between them but always stayed in motion. - 
  
  1743-1794
He proved the law of conservation - 
  
  1754-1826
He was known for proving that every pure compont consists of elements in a definite proportion - 
  
  1766-1844
saId that chemical reactions can be explained by the union and separation of atoms, and that these atoms have characteristic properties. have five assuptions to his theory - 
  
  1852-1908
while doing an experiment of the exposure of a uranium bearing ccrytal to sunlight; he discovered radioactivity. - 
  
  was interested in Henri becquerel experimenttts and end up finding two new radioactive elements
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  was able to measure the rays of cathode rays at which they were deflected, and then caculated the ratio of the electrical charge tot the mass of the particles.
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  found that atoms are mainly made up of empty space. became known as the father of nuclear physics
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  measured the charge of an electron
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  He discovered the neutron