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Johann Dobereiner
He classified some elements into groups of three (triads). The elements in a triad had similar chemical properties and orderly physical properties - model of triads -
John Newlands
In 1863, he suggested that elements be arranged in octaves because he noticed (after ordering the elements in increasing atomic mass) that certain properties repeated every 8th element - Law of octaves. -
Dmitri Mendeleev
In 1869, he published a table of the elements organised by increasing atomic mass. -
Lothar Meyer
In 1869, he also published a table of the elements organised by increasing atomic mass. -
Henry Moseley
In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements. He rearranged the elements in increasing atomic number. -
Glenn T. Seaborg
After co-discovering 10 new elements, in 1994 he moved 14 elements out of the main body of the periodic table to the Actinoids series. He also had an element named after him while he was still alive.
