What chemical properties of elements were used by Mendeleev in creating his periodic table ?

Would you place the two isotopes of chlorine, C1-35 and C1-37 in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answer.

State Mendeleev’s periodic law.

State any three limitations of Mendeleev’s classification of element.

Besides gallium, which two other elements have since been discovered for which Mendeleev had left gaps in his periodic table.