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Dalton publishes his Atomic Theory, stating that all matter is composed of small, invisible atoms. http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html http://scienceworld.wolfram.com/biography/pics/Dalton.jpg
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Eugene Goldstein discovered a postive particle with an equal and opposite charge to the negative. He named this particle the proton.
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Thomson discovered that cathode rays were negatively charged, and determined that atoms were also negatively charged. He renamed cathode ray s electrons, and developed a model of an atom which was a positively charged sphere with negatively charged electrons stuck in it. http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html http://upload.wikimedia.org/wikipedia/commons/c/c1/J.J_Thomson.jpg
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By sending a radioactive wave through a magnetic field, Rutherford determined there were three types of radioactivity: Alpha particles (+), beta particles (-), and gamma rays (0). He also created a new atomic model which was mostly empty space with a tiny nucleus with electrons swirling around it. His model replaced Thomson's. http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1908/rutherford.jpg
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Niels Bohr proposed an atomic model with a small nucleus orbited by electrons travelling in a circular motion, which was a result of electric charge, not gravity. http://en.wikipedia.org/wiki/Bohr_model http://upload.wikimedia.org/wikipedia/commons/thumb/6/6d/Niels_Bohr.jpg/180px-Niels_Bohr.jpg
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Henry Moseley tries to determine the number of protons in the atomic nucleus using x-rays, but to no avail. His failure was due to the fact that neutron had not yet been discovered. http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html http://www.windows2universe.org/physical_science/physics/atom_particle/atomic_nucleus_sm.jpg
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It was discovered, by Irene Curie and Frederic Joliot-Curie that by bombarding certain elements with alpha particles, artificial and radioactive elements could be created. For this discovery, they recieved the 1935 Nobel Prize. http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html
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In >430 BC<, Democritus proclaimed that the smallest unit of matter was the atom. This is a shocking thing to hear coming from a man who believes the sun in a horse-drawn chariot. http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html
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http://en.wikipedia.org/wiki/Alchemy An ancient form of chemistry, alchemists labored to create the philosopher's stone, which could turn lead into gold. This was before it was known that elements could not be transformed into other elements. The practice died out sometime in the 19th century.
