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The disproving of Aristotle's four-elements theory and the publishing of the book, The Skeptical Chemist (by Robert Boyle), combined to destroy this early form of chemistry.
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Description Source</a>John Dalton publishes his Atomic Theory which states that all matter is composed of atoms, which are small and indivisible.
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Eugene Goldstein discovered positive particles by using a tube filled with hydrogen gas. The positive particle had a charge equal and opposite to the electron. It also had a mass of 1.66E-24 grams or one atomic mass unit. The positive particle was named the proton.
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Wilhelm Roentgen accidentally discovered x-rays while researching the glow produced by cathode rays. He discovered that the rays that were causing the fluorescence could also pass through glass, cardboard and walls. The rays were called x-rays.
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J.J. Thomson placed the Crookes' tube within a magnetic field. He found that the cathode rays were negatively charged. He concluded that all atoms have this negative charge (through more experiments) and he renamed the cathode rays electrons. His model of the atom showed a sphere of positively charged material with negative electrons stuck in it.
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Robert Millikan discovered the mass of an electron by introducing charged oil droplets into an electrically charged field. Millikan found the mass of one electron to be 9.11E-28 grams. -
Ernest Rutherford sent a radioactive source through a magnetic field. Some of the radioactivity was deflected to the positive plate; some of it was deflected to the negative plate; and the rest went through the magnetic field without deflection. Thus, there were 3 types of radioactivity. The Thomson model was thrown out after the Rutherford model.
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The Bohr model of the atom introduces the theory that electrons travel in discrete orbits around the atom's nucleus.
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Descript SourcePicture SourceAlbert Einstein and Enrico Fermi both warned the United States about Germany's extensive research on atomic fission reaction. Below the football field at the University of Chicago, the United States developed the very first working nuclear fission reactor.
