(a) State the merits of Mendeleev’s classification of elements. (b) Describe two anomalies of Mendeleev’s periodic classification of elements.
(a) State the merits of Mendeleev’s classification of elements. (b) Describe two anomalies of Mendeleev’s periodic classification of elements.

(a) Merits:

1. Predicted the existence of certain elements such as gallium, scandium and germanium.

2. Predicted the properties of various elements based on their positions in the periodic table.

3. Mendeleev’s periodic table could place the group 18 elements known as noble gases in the periodic table.

(b) 1.This could not explain the position of isotopes having same chemical properties but different atomic masses in the periodic table. So the isotopes of same element should be given different place in periodic table and arranged in increasing order of their atomic masses

2. Mendeleev’s periodic table could not assign a proper position to hydrogen.