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100
Matter is not made of atoms
Contrary to many of his time, Aristotle believed matter was not made of atoms. -
100
Matter is made of atoms
Early Greek philosphers, such as Democritus and Leucippus, contrary to many beleifs, believed matter is made of atoms. -
Period: 100 to
History of Chemistry
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Trying to turn base metals into gold
The Alchemists were people who claimed that their scientific practices were the precursors to profound powers. One of their actions was trying to turn base metals into gold. -
Law of Conservation of Mass
Antoine Lavoisier stated that that matter can be changed from one form into another, mixtures can be separated or made, and pure substances can be decomposed, but the total amount of mass stays constant. -
Atomic Theory
John Dalton proposed an atomic theory with spherical solid atoms based upon measurable properties of mass. -
Law of Definite Proportions
Joseph Proust stated that a chemical compound always contains exactly the same proportion of elements by mass. -
Discovery of radioactivity
Henri Becquerel, when studying the properties of x-rays, proved that uranium emitted radiation without an external source of energy. This was the discovery of radioactivity. -
Discovery of electron using a cathode ray tube
J.J. Thompson placed cathode tubes in electric and magnetic fields. The cathode rays bent, so he knew there were particles, electrons. -
Discovery that energy is given off in "packets" called quanta or photons
As an explanation for electrons losing energy, Max Planck said that energy, at the sub-atomic level, can only be transfered in small units, quanta or photons. -
Discovery of radioactivity with radium and uranium
Marie and Pierre Curie noticed radioactivity in unique minerals with radium and uranium. -
Origin of energy from nuclear experiments
Albert Einstein discovered the origin of energy from nuclear experiments, otherwise known as E=mc^2, the relativity equation. This means that energy is equal to mass multiplied by the speed of light squared. -
Period: to
History of Chemistry
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Discovery that the atom hass a nucleus
While Ernest Rutherford was a professor at Manchester, he announced each atom has a nucleus. This ultimately led to the splitting of the aton, 20 years later -
Charge of the electron from the oil drop experiment
Robert Millikan, performing his oil drop experiement, was able to discover the charge of an electron. -
Discovery of each element having its own atomic number
Henry Moseley used equipment he built himself to discover that each element has its own atomic number. -
Discovery that electrons exist at different distances from the nucleus
Niels Bohr proposed a model for the hydrogen atom, showing that electrons orbit around the nucleus at different distances -
Discovery of neutron
James Chadwick used scattering data to calculate the mass of this neutral particle, discovering the neutron. -
Discovery of nuclear fission
Lise Meitner, Otto Hahn, and Fritz Straussman all contributed to the discovery of nuclear fission, during the second World War. -
Development of multiscale models for complex chemical systems
Martin Karplus, Michael Levitt, and Arieh Warshel by developing these models, made it possible to simulate the dynamics of complext chemical systems.
