Mendeleev was a Russian chemist, who contributed the most for the development of periodic table of elements wherein the elements were arranged on the basis of their fundamental property, the atomic mass and also on the similarity of chemical properties. Only 63 elements were known at his time. He arranged the 63 elements in the increasing order of their atomic masses and found that there was a periodic recurrence of elements with similar physical and chemical properties, He observed that elements with similar properties fall in the same vertical column. These vertical columns are called groups and horizontal rows of elements are called periods. Mendeleev predicted the existence of certain elements not known at that time and named two of them as Eka-silicon and Eka-aluminium.
Mendeleev arranged the periodic table on the basis of their fundamental property:

Options

A. Atomic mass
B. Atomic number
C. Number of neutrons
D. Valence electrons

Answer

A

Explanation

Mendeleev arranged the known elements according to increasing order of their atomic masses because according to him fundamental properly of an element was atomic mass.