Elements which are similar as regards their chemical properties have atomic weights which are either of nearly the same value (eg. Pt, Ir, Os) or which increase regularly (eg. K, Ru, Cs).
Dmitri MendeleevThe elements, if arranged according to their atomic weights, exhibit an apparent periodicity of properties.
Dmitri MendeleevThe most all penetrating spirit before which will open the possibility of tilting not tables, but planets, is the spirit of free human inquiry. Believe only in that.
Dmitri MendeleevWhy do they [Americans] quarrel, why do they hate Negroes, Indians, even Germans, why do they not have science and poetry commensurate with themselves, why are there so many frauds and so much nonsense? I cannot soon give a solution to these questions ... It was clear that in the United States there was a development not of the best, but of the middle and worst sides of European civilization; the notorious general voting, the tendency to politics... all the same as in Europe. A new dawn is not to be seen on this side of the ocean.
Dmitri Mendeleev