Answer: The number of series in Mendeleev's Periodic table is 12.
Explanation:
Horizontal rows present in the periodic table are called periods. Vertical rows in the periodic table are called series.
Mendeleev gave periodic table in the year 1869 by arranging elements according to their atomic weights a in tabular form.
Mendeleev's periodic table depicts 12 periods/series.
Thus, we can conclude that the number of periods/series in Mendeleev's Periodic table is 12.
