Question

What physical and chemical properties of elements were used by Mendeleev in creating his periodic table? List two observations which posed a challenge to Mendeleev's Periodic Law.

Answer 1

The physical property used was the atomic mass of an element.

The chemical property used was the nature of oxide and hydride formed( i.e. similarity in chemical properties were used by Mendeleev).

The two observations that posed challenge in Mendeleev Periodic Law were:

(i) Arranging elements according to the increasing order of atomic mass could not be maintained. Chemical properties do not depend on atomic mass.

(ii) Isotopes were not given any place in the table as they have different atomic mass but same chemical properties.