During his regular lecture for students at the University of Sankt Petersburg, on
17 February 1869, Dmitri Ivanovič Mendeleev has outlined, from methodical
reasons (!) the first version of the periodic system of chemical elements represented
in the following figure.
First outlines of the periodic system of elements of Dimitri Ivanofič Mendeleev
Dmitri Ivanovič Mendeleev (1834–1907)
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10 Systematization, Classification, Structure, and Elements