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Berzelius classified minerals according to their chemical composition http://chemistry.about.com/cs/history/a/aa020204a.htm
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Publishes atomic theory: all matter is composed of atoms, which are small and invisable http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html http://www.brianmicklethwait.com/education/archives/001361.htm
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Heinrich Geissler created the first vacuum tube. http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html http://en.wikipedia.org/wiki/Heinrich_Gei%C3%9Fler
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Henri Becquerel discovered the pitchblend property of elements
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Marie Curie discovered Uranium and Thorium http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html
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Sir Joseph John Thomson discovered electrons http://www.chemistryexplained.com/Te-Va/Thomson-Joseph-John.html
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Rutherford concluded that the atom was mostly empty space by sending radioactive particles through gold he also discovered the three types of radiation (alpha, beta, and gamma) http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html http://cascience6.wikispaces.com/Ernest+Rutherford+09
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Bohr created a model of the atom that showed negatively charged electrons around the positive nucleus http://chemistry.about.com/b/2011/10/06/on-this-day-in-science-history-october-7-bohr-model.htm http://en.wikipedia.org/wiki/Niels_Bohr
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Irene Curie and Frederic Joliot-Curie discovered radioactive elements that could be created in a lab http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html http://en.wikipedia.org/wiki/Radioactive_decay
