Question

How did the position of isotopes pose a problem in mediaeval periodic table how was the problem solved

Answer 1

in modern periodic table isotopes is placed in the slot of metals like chlorine has a isotope it placed with its metal

Answer 2

Isotopes were discovered long after Mendeleev had proposed the classification of element and isotopes had same chemical properties but different atomic masses so all the elements of isotopes posed a challenge to Mendeleev’s periodic law