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460 BC
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The start of chemistry. Democritus was a Greek philosopher and scientist. Only some parts of his work are left, he added to the theory of atomism, by suggesting that all matter consisted of tiny, indivisible particles.
384 BC - 322 BC
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Aristotle recognized that most ordinary, material things are composed of multiple substances, although he thought that some of them could be composed of a single, pure substance. He then used elemental theory to account for many properties of substances. For example he distinguished between liquids and solids. He further distinguished liquids from gases, which don't even have their own volume.
300 BC - 300 BC
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A type of chemistry and philosophy practiced in the Middle Ages, this is discovering methods for transmuting baser metals into gold and finding a universal solvent and universal cure for disease for the human body.
1667
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Phlogiston, in early chemical theory, principle of fire, which every combustible substance was in part composed. The major objection to the theory, that ash of organic substances weighed less than the original while the calx was heavier than the metal, was a major part to Stahl, who thought of phlogiston as an immaterial “principle” rather than as an actual substance. As chemistry advanced, phlogiston was considered a true substance, and much effort was expended in accounting for the weight changes observed. When hydrogen, very light in weight and extremely flammable, was discovered, some thought it was pure phlogiston.
1743 - 1794
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Lavoisie established the law of conservation of mass, determined that combustion and respiration are caused by chemical reactions, he named “oxygen,” and helped systematize chemical nomenclature, along with many other accomplishments.
1752 - 1752
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Benjamin Franklin performed an incredibly dangerous experiment. In order to show that lightning is a form of electricity, he flew a kite in a thunderstorm with a key attached. The key drew off electricity from the thunderclouds, and Franklin could feel a shock from the key, demonstrating that it had collected static electricity.
1754 - 1754
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Joseph-Louis Proust, also known as Luis Proust, French chemist who proved that the relative quantities of any given pure chemical compound’s constituent elements remain invariant, regardless of the compound’s source. This is known as Proust’s law, or the law of definite proportions (1793), and it is the fundamental principle of analytical chemistry. Proust also carried out important applied research in metallurgy, explosives, and nutritional chemistry.
1766 - 1844
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John Dalton is best known for his pioneering theory of atomism. Dalton also developed methods to calculate atomic weights and structures and formulated the law of partial pressures. He kept daily weather records from 1787 until his death, including a notebook that had independent thoughts stating atomic weights and compositions of compounds.
1898 - 1898
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John discovered the electron and then went on to propose a model for the structure of the atom. His work also led to the invention of the mass spectrograph. John also preformed a series of experiments in 1897 designed to study the nature of electrical discharge, an area being investigated by many scientists at the time.
1903 - 1903
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Becquerel's earliest work was concerned with the plans polarization of light, and the absorption of light by crystals. He also worked on the subject of terrestrial magnetism. Some of Henri's previous work was overshadowed by his discovery of natural radioactivity
1903 - 1903
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French was the first women to win a Nobel prize and the only women to win the award in two different fields. (Physics and Chemistry) this led to the discovery of polonium and radium and after Pierre's (husband) the further development of X-Rays. They began researching many things on elements
1910 - 1910
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Physicist Ernest Rutherford established the nuclear theory of the atom, during the experiment Rutherford shot a beam of alpha particles at a sheet of gold foil, a few of the particles deflected from the beam. Which concluded that a tiny, dense nucleus was causing the deflections from the beam.
1910 - 1910
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Millikan was honored with a Nobel Prize for Physics, for his study of the elementary electronic and the photoelectric effect. In 1909 he began a series of experiments to determine the electric charges carried by a single electron. Which began by measuring the course of charged water droplets in an electrical field. Results told Millikan that the charge on the droplets is a multiple of the elementary electrical charge, but the experiment was not accurate enough to be convincing.
1935 - 1935
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In 1932, Chadwick observed that beryllium, when exposed to bombardment by alpha particles, released an unknown radiation that in turn ejected protons from various substances. This discovery provided a new tool for inducing atomic disintegration, since neutrons, being electrically charged, could penetrate undeflected into the atomic nucleus