We must expect the discovery of many as yet unknown elements-for example, elements analogous to aluminum and silicon- whose atomic weight would be between 65 and 75.
Dmitri MendeleevIf all the elements are arranged in the order of their atomic weights, a periodic repetition of properties is obtained. This is expressed by the law of periodicity.
Dmitri MendeleevKnowing how contented, free, and joyful is life in the world of science, one fervently wishes that many would enter its portals.
Dmitri Mendeleev