When Mendeleev started his work,the number of known elements were:

Mendeleev predicted the existence of certain elements not known at that time and named two of them as Eka-silicon and Eka-aluminium.
$(a)$ Name the elements which have taken the place of these elements.
$(b)$ Mention the group and the period of these elements in the Modern Periodic Table.

State whether the following statement is true or false: In $1913$,Dmitri Ivanovich Mendeleev showed that the atomic number of an element is a more fundamental property than its atomic mass.

Which group of elements could be placed in Mendeleev's Periodic Table without disturbing the original order? Give reason.

What type of oxide would Eka-aluminium form?

Write true or false for the statement: In Mendeleev's periodic table,elements were arranged in the order of their increasing atomic masses and it was also observed that there occurs a periodic recurrence of elements with similar physical and chemical properties.