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Aristotle proposed the four element theory which consisted of: Earth, Air, Water, and Fire.
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Democritus and Leucippus propose the idea of an atom which they believe is an invisible particle in which everything is made up of.
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Sir Francis Bacon published 'The proficience and advancement of learning' which contained a description of what would later be known in future as 'The Scientific Method'.
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Hennig Brand attempted to create a Philosopher's Stone; an object which could turn metals into gold. He heated residues and a liquid dropped out and burst into flames. This was the discovery of Phosphorous.
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Joseph Black isolated Carbon Dioxide and referred to it as 'fixed air'.
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Carl Wilhelm Scheele and Joseph Priestly isolate the element of Oxygen
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Henry Cavendish discovered Hydrogen and describes it as a colourless, odourless gas that burns and can form an explosive mixture with air.
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Antoine Lavoisier wrote the first list of elements which contained 33 elements and identified the metals and non-metals.
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John Dalton proposed the 'Dalton Law' which describes the relationship between the components in a mixture of the gases.
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Jakob Berzilius developed a table of atomic weights and introduced letters to symbolise different elements.
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Johann Dobereiner developed groups of 3 elements with similar properties
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John Newlands arranged the known elements in order of atomic weights and observed some similarities between different elements.
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William Ramsay discovered the Noble Gases.
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Ernest Rutherford discovered the source of radioactivity as decaying atoms
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Henry Moseley determined the atomic number of each of the elements and modified the 'Periodic Law'.
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Glenn Seaborg synthesised transuranic elements which are all the elements after Uranium.
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Edwin McMillan and Philip H. Abelson identify neptunium, the lightest and first synthesized transuranium element, found in the products of uranium fission.