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Antoine Laviosier drew the first periodic table. This contained 33 different elements.
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in 1817 Johan Dobereiner discovered that stroniums atomic weight falls exactly between the atomic weights of calcium and barium,
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Alexandre-Emile Béguyer listed the known elements and to a strip of paper and wound them around a cylinder. Groups of 3 elements with similar properties appeared together down the cylinder. This was called the telluric screw
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John Newlands organised the elements in order of increasing atomic weight.
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John Newlands noted down on paper that after each interveal of 8 elements a recurrence of properties appears
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Dimitri Mendeleev made a periodic table in order or atomic weight. But he arranged them periodically so that rows had similar properties, coloumns had similar properties and the diagonally they had similar properties
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Lord Rayleigh discovered Argon
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William Ramsey Suggests that argon gets placed between Chlorine and Potassium dispite the fact that Potassium had a greater atomic weight than Argon
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Mosely arranged the elements by atomic number rather than atomic mass. This is how it is organised currently.
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Glenn Seaborg artificially produces Neptunium which is known as a heavy mass element