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Introduced the four elements theory:
Earth, Air, Fire, Water -
He introduced the idea of an atom
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He introduced The Proficience and Advancement of Learning which contained a description of what would later be known as the scientific method
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Published the Skeptical Chemist
also had some of the earliest thouhts about atoms -
Discovered Hydrogen as a colorless odourless gas that burns and can form an explosive mixture with air
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wrote the first extensive list of elements containing 33 elements & distinguished between metals and non-metals
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developed a table of atomic weights & introduced letters to symbolize elements
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arranged the known elements in order of atomic weights & observed similarities between some elements
Lothar Meyer develops an early version of the periodic table, with 28 elements organized by valence
Dmitri Mendeleev produced a table based on atomic weights but arranged 'periodically' with elements with similar properties under each othe -
discovered the Noble Gases
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isolated radium and polonium from pitchblende
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discovered the source of radioactivity as decaying atoms
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determined the atomic number of each of the elements and modified the 'Periodic Law