The first table Mendeleev created contained fixed positions for several new chemical elements based on the calculated relative atomic mass for each of them. In 1871 the scientist named three of these elements (ekaboron, ekaaluminum, ekasilicon) and assumed what their properties would be on the basis of their place in the periodic system.

The validity of the periodic law was confirmed by the discovery of three chemical elements as they were previously very accurately defined by D. Mendeleev:

•  Gallium Ga (z = 31), discovered in 1875 by the French chemist Paul Emile Lecoq de Boisbaudran;
•  Scandium Sc (z = 21), discovered in 1879 by the Swedish chemist Lars Fredrik Nilson;
•  Germanium Ge (z = 32), discovered in 1886 by the German chemist Clemens Alexander Winkler.

 

Did you notice the difference in the arrangement of the chemical symbols of the elements in the first Mendeleev table and the one used nowadays?

 

 

 

Problem 9. In the periodic table, please find the chemical symbol of the element Gallium or Germanium (whichever you choose) and define in which period and in which group the element you have chosen is situated, and what its valence to hydrogen and to oxygen is.

Try to figure out why when D. Mendeleev found the place of these elements, he named them ekaaluminum and ekasilicon.