After the Actinides, then what?

摘要

Mendeleev's creation of the Periodic Table depended on the discovery of a considerable number of chemical elements in the preceding century. A key element in his scheme was its basis on patterns and trends in physical and chemical properties (and not, as chemists unconsciously (but frequently) seem to assume, quantum mechanics). This meant that he was able to recognise that iodine belonged in Group Ⅶ with the halogens, rather than with the chalcogenides in Group Ⅵ; further, he left gaps for as yet undiscovered elements, such as eka-boron (Sc), eka-silicon (Ge) and eka-aluminium (Ga), for which he was able to propose properties, based upon interpolation between those of the known elements.