Question

Which‌ ‌eka‌ ‌silicon‌ ‌element‌ ‌was‌ ‌predicted‌ ‌by‌ ‌Mendeleev?‌

Answer 1

Hint: Mendeleev gave a periodic table based on the number of protons and neutrons, he clubbed all elements which have similar properties and arranged them according to increasing atomic weight. Atomic weight is defined as the weight of the one atom or molecule.

Complete answer:
Mendeleev gave a periodic table based on the number of protons and neutrons, he clubbed all elements which have similar properties and arranged them according to increasing atomic weight. He grouped the elements according to their similarity in properties, he arranged all elements in the increasing order of their similar properties and atomic mass.
He left some gaps in the periodic table in hope for their future discovery. He named these elements Eka silicon and Eka aluminium. There were many elements that were not able to get discovered because of the lack in technology and vision by Mendeleev believed that once these elements would be discovered and will find their place in the periodic table.
Eka silicon came to be known to be known as germanium.
Silicon has the electronic configuration as follows: $[Ne]3{s^2}3{p^2}$
Germanium has the electronic configuration as: $[Ar]3{d^{10}}4{s^2}4{p^2}$
Their last orbital electronic configuration is the same, which means they have the same number of electrons and therefore they belong to the same group of the periodic table.
Germanium or Eka silicon was predicted by Mendeleev.

Note:
Mendeleev also predicted the existence of elements of the analogue of manganese, tellurium, iodine, barium. Some other elements were discovered later. After that also came too many radioactive elements which had a table outside the periodic table.