Mendeleev's predicted elements
Dmitri Mendeleev published a periodic table of the chemical elements in 1869 based on properties that appeared with some regularity as he laid out the elements from lightest to heaviest. When Mendeleev proposed his periodic table, he noted gaps in the table and predicted that as-then-unknown elements existed with properties appropriate to fill those gaps. He named them eka-boron, eka-aluminium and eka-silicon with atomic masses 44, 68 and 72 respectively.
Edward G. Mazurs
A revised "centenary" edition covering a full 100 years of periodic tables was republished under the title "Graphic Representations of the Periodic System During One Hundred Years " in 1974. Mazurs provided a comprehensive analysis and classification of periodic tables, listing and classifying over 700 periodic tables. He recommended Charles Janet's left-step system and suggested that it could be expanded into three dimensions.