(a) Which two criteria did Mendeleev use to classify the elements in his periodic table ? (b) State Mendeleev's periodic law. (c) Why is it not possible to give a fixed position to hydrogen in Mendeleev's periodic table ?

(a) Which two criteria did Mendeleev use to classify the elements in h

1.	(a) Which two criteria did Mendeleev use to classify the elements in his periodic table ? (b) State Mendeleev's periodic law. (c) Why is it not possible to give a fixed position to hydrogen in Mendeleev's periodic table ?
Answer» Solution :(a) (i) Increasing order of atomic mass as physical properties and similarities in chemical properties of elements. (II) The formulae and nature of hydrides and OXIDES formed by elements was TREATED as basic chemical properties for its classification. (b) Mendeleev.s Periodic Law : The properties of elements are the periodic function of their atomic masses. (C) It is because it RESEMBLES both with alkali metals as well as halogens.