The number of groups and periods in Mendeleev's periodic table are

According to Mendeleev's Periodic Law, an element's properties are a periodic function of its atomic mass.

Mendeleev tabulated all 63 elements (found up to his time) and organized them in ascending order of increasing relative atomic masses. Mendeleev's Periodic Table is the name of it. Eight vertical columns and seven horizontal rows were used to divide the table. These rows are referred to as periods and these columns are as groups.