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Aristotle proposes the four element theory: earth, air, fire & water
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Sir Francis Bacon published "The Proficience and Advancement of Learning" which contained a description of what would later be known as the scientific method.
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Joseph Black isolated carbon dioxide, which he called "fixed air".
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Henry Cavendish discovered hydrogen as a colorless, odourless gas that burns and can form an explosive mixture with air
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Carl Wilhelm Scheele and Joseph Priestly independently isolated oxygen
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Jakob Berzelius developed a table of atomic weights & introduced letters to symbolize elements
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A.E.Beguyer de Chancourtois was the first person to make use of atomic weights to reveal that the elements were arranged according to their atomic weights with similar elements occurring at regular intervals.
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John Newlands, an English chemist, proposed the Law of Octaves which stated that elements repeated their chemical properties every eighth element.
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Lothar Meyer develops an early version of the periodic table, with 28 elements organized by valence
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Henry Moseley determined the atomic number of each of the elements and modified the 'Periodic Law'.
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William Ramsay discovered the Noble Gases.
