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Johann Dobereiner
Organised the elements into threes and propsed the 'Model of the Triads 'Theory -
John Newlands
Devised the 'Law of Octaves' Theory. However this theory was ridiculed as it did not work beyod the chemical Calcium. -
Dmitri Mendeleev and Lothar Meyer
Both Devised a table that arranged chemicals in order of lightest to heaviest via atomic weight. -
Henry Moseley
Discovered the atomic mass of all known elements. He then Rearranged the table in order of Atomic Number rather than weight -
Glenn Seaborg
Co-discovered 10 new elements and then rearranged the table to take out 14 elements and placed them below the lactinides. These elements became the Actinides.