Mendeleev, completing his final version of the…

Mendeleev, completing his final version of the periodic table in 1871, finds it necessary to leave a blank at the position now occupied by scandium.

He accurately predicts the qualities of what he calls ekasilicon, ekaaluminium and ekaboron (germanium, gallium and scandium, respectively.

For his predicted eight elements, he uses the prefixes of eka, dvi, and tri (Sanskrit one, two, three) in their naming.

Mendeleev questions some of the currently accepted atomic weights (they can be measured only with a relatively low accuracy at this time), pointing out that they do not correspond to those suggested by his Periodic Law.

He notes that tellurium has a higher atomic weight than iodine, but he places them in the right order, incorrectly predicting that the accepted atomic weights at the time are at fault.

He is puzzled about where to put the known lanthanides, and predicts the existence of another row to the table: the actinides, which are some of the heaviest in atomic mass.