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330
Aristotle - Four element theory: earth, air, fire & water
Four element theory: earth, air, fire & water -
Antoine Lavoisier- Wrote the first extensive list of elements containing 33 elements.Distinguished between metals and non-metals.
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Jöns Jakob Berzelius - Developed a table of atomic weights.Introduced letters to symbolize elements
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Johann Döbereiner - Developed 'triads', groups of 3 elements with similar properties.Lithium, sodium & potassium formed a triad.Calcium, strontium & barium formed a triad.Chlorine, bromine & iodine formed a triad.
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John Newlands - The known elements (>60) were arranged in order of atomic weights and observed similarities between the first and ninth elements, the second and tenth elements etc. He proposed the 'Law of Octaves'.
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Lothar Meyer - Compiled a Periodic Table of 56 elements based on the periodicity of properties such as molar volume when arranged in order of atomic weight.
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Dimitri Mendeleev - Produced a table based on atomic weights but arranged 'periodically' with elements with similar properties under each other
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William Ramsay - Discovered noble gases
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Glen Seaborg - Synthesised transuranic elements (the elements after uranium in the periodic table)