Historedia
Episode 3 of 3

Prediction of Unknown Elements

When
1870
Where
Saint Petersburg
Part of
Mendeleev completes and presents the periodic table

Mendeleev used gaps in his 1869 table to predict properties of missing elements, and in 1870 gave detailed predictions for three eka-elements.

Mendeleev successfully used the periodic law to predict properties of missing elements. In 1870 he first tried to characterize the yet undiscovered elements, giving detailed predictions for three he termed eka-boron, eka-aluminium, and eka-silicium, corresponding to scandium, gallium, and germanium, which were realized later.

Sources

  1. Periodic table Wikipedia, revision of 2026-09-21
  2. Dmitri Mendeleev Wikipedia, revision of 2026-10-05
  3. History of the periodic table Wikipedia, revision of 2026-10-05

Machine-drafted from the cited Wikipedia passages and checked by a reviewing model, not by a human editor. Every passage cites the revision it was written from; dates and places follow those passages.