Question

Q.1 - State Mendeleev Periodic Law.
Q.2- Write the Merits of Mendeleev's Periodic Table .
Q.3-Write the Demerits of Mendeleev's Periodic Table .​

Answer 1

Q. State Mendeleev's Periodic Law.

★ Mendeleev's periodic law states that: The physical and chemical properties of elements are a periodic function of their atomic masses.

Q. What are the merits of Mendeleev's Periodic Law?

★ Merits of Mendeleev's Periodic Table are:

(i) Mendeleev left some gaps in his table. Predicted the chemical properties of these elements which were discovered later and had same properties as predicted.

(ii) He arranged the elements very systematically in periods and groups.

Q. What are the demerits of Mendeleev's Periodic Law?

Demerits of Mendeleev's Periodic Table :

(i) Mendeleev arranged elements in the ascending order of their atomic masses. There was no fixed position for hydrogen in his periodic table, as it resembled alkali metals as well as halogens.

(ii) Elements of higher atomic mass were placed before elements of lower atomic mass. Cobalt with atomic mass 58.93 was placed before nickel with atomic mass 58.71.

(iii) Elements having different properties were placed in the same sub group like manganese (Mn) was placed with halogens which had totally different properties.