What characteristic of Mendeleev 's periodic table implicitly predicted the properties of elements that had not yet been discovered ?
The four predicted elements lighter than the rare earth elements , " ekaboron " ( " Eb " ) , " ekaaluminium " ( " Ea " ) , " ekamanganese " ( " Em " ) , and " ekasilicon " ( " Es " ) , proved to be good predictors of the properties of scandium , gallium , technetium and germanium respectively , which each fill the spot in the periodic table assigned by Mendeleev .