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Antoine-Laurent de Lavoisier
Lavoiser groups elements into metals and nonmetals based on their physical properties. -
Johann Dobereiner
He begins to group elements with simlar properties in to groups of three or triads. -
Johann Dobereiner
Dobereiner discovered the halogen triad made up of chlorine, bromine and iodine and a alkali metal triad of lithim, sodium and potassium -
John Newlands
In 1864, English chemist John Newlands noticed that, if the elements were arranged in order of atomic weight, there was a periodic similarity every 8 elements. He proposed his ‘law of octaves’ on this. -
Lothar Meyer
In 1864, Lothar Meyer created a textbook that included an abbreviated version of a periodic table used to classify about half of the known elements. -
Lothar Meyer
In 1868, Meyer constructed am extended table which he gabe to a colleague for evaluation. -
Dimitri Mendeleev
In 1869, Russian chemist Dmitri Mendeleev produced a periodic table based on atomic weights but arranged ‘periodically’. Elements with similar properties appeared under each other. Gaps were left for yet to be discovered elements. -
Henry Moseley
In 1914, Henry Moseley determined the atomic number of each of the known elements. He realised that, if the elements were arranged in order of increasing atomic number rather than atomic weight, they gave a better fit within the ‘periodic table’. -
Glenn Seaborg
Seaborg discovered the transuranium elements, atomic numbers 94-102