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Aristotle proposed the four element theory: earth, air, fire & water
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NOTE: Any events without a specific date (aside from the year) are marked with "Jan 1"
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Plato coined the term ‘elements’ (stoicheia)
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Democritus and Leucippus proposed the idea of the atom, an invisible particle that makes up all matter .
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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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Robert Boyle published “The Sceptical Chymist”, a treatise on the distinction between chemistry and alchemy. It also contained some of the earliest ideas of atoms, molecules, and chemical reaction marking the beginning of the history of modern chemistry .
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Phosphorus was first discovered using scientific reasoning by Hennig Brand.
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Henry Cavendish discovered Hydrogen as colorless, odourless gas that burns and can form an explosive mixture with air .
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Antoine Lavoisier wrote the first extensive list of elements containing 33 elements & distinguished between metals and non-metals.
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John Dalton proposed “Dalton’s Law”, describing the relationship between components in a mixture of gases .
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47 elements were discovered, and scientists began to see patterns in the characteristics
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Johann Dobereiner grouped elements with similar properties into groups of three or triads. According to him, nature contained triads of elements, where the middle element had properties that were an average of the other two elements
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Jakob Berzelius developed a table of atomic weights and introduced letters to symbolise elements.
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A.E. Beguyer de Chancourtois was the first to incorporate atomic weights to reveal that elements were arranged according to their atomic weights, with similar elements occurring at regular intervals.
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John Newlands proposed Law of Octaves; where he stated that elements repeated their chemical properties every eighth element.
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Lothar Meyer developed an early version of the periodic table, with 28 elements in order of their atomic weight.
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John Newlands arranged 56 elements into 11 groups based on characteristics & observed similarities between some elements.
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63 elements have been discovered
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Mendeleev's Periodic Table was the first published periodic table in "On the Relationship of the Properties of the Elements to their Atomic Weights." He left gaps for undiscovered elements, predicting what the properties of these undiscovered elements might be.
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Antoine Bequerel discovered radioactivity.
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William Ramsay discovered the noble gases. He realised that they represented a new group in the periodic table.
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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. He realised that arranging the elements in order of increasing atomic number rather than atomic weight gave a better fit within the periodic table.
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Rutherford first identified protons in the atomic nucleus.
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James Chadwick first discovered neutrons.
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Glenn Seaborg discovered the transuranium elements, atomic numbers 94 to 102. He also redesigned the periodic table to its current form after the completion of actinide series
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Edwin McMillan and Philip H. Abelson identified neptunium, the lightest and the first synthesized transuranium element, found in the products of uranium fission.
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Glenn Seaborg discovered plutonium
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Glenn Seaborg artifically produced heavy mass elements such as neptunium. These new elements were part of a new block of the periodic table called 'actinides.'
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Glenn Seaborg identified lanthanides and actinides, placing it below the periodic table.
