Dmitri Mendeleev
Dmitri Ivanovich Mendeleev was born February 8, 1834 in Verkhnie Aremzyani, in the Russian province of Siberia. His family was unusually large.
In 1869, just five years after John Newlands put forward his law of octaves, a Dmitri Mendeleev published a periodic table. He arranged the elements known at the time in order of relative atomic mass.
He realized that the physical and chemical properties of elements were related to their atomic mass, and arranged them so that the groups of elements with similar properties fell into vertical columns in his table. However this meant that there were gaps in the periodic table. Mendeleev thought that this meant that it was because it belonged to elements that have not been discovered yet.
He found out the atomic mass of the missing elements, and predicted their properties. Which turned out to be true.
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Alexandre-Emile Béguyer de Chancourtois
Alexandre-Emile Beguyer de Chancourtois was a French geologist and mineralogist born on January 20, 1820 – died on November 14, 1886. De Chancourtois was the first to arrange the chemical elements in order of atomic weights.
He devised an early form of periodic table, which he called the telluric helix because the element telluriumcame in the middle. It was also some what appropriate coming from a geologist as the element tellurium is named after the Earth. de Chancourtois created a fully functioning and unique system of organizing the chemical elements. His proposed classification of elements was based on the newest values of atomic weights obtained by Stanislao Cannizzaro in 1858.
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