Question

demerits of Mendeleeve periodic laws​

Answer 1

ANSWER:

MENDELEEV PERIODIC LAW:

Mendeleev treated formulae of hydrides and oxides as one of the basic criteria for categorization. He took 63 cards and on each card, he wrote the properties of one element. He grouped the elements with similar properties and pinned it on the wall. He observed that elements were arranged in the increasing order of atomic mass and there was the periodic occurrence of elements with similar properties.

MERITS OF MENDELEEV PERIODIC LAW:

⇒ Some gaps were left for the elements yet to be discovered. Thus, if a certain new element is discovered, it can be placed in a new group without disturbing any existing group.

DEMERITS OF MENDELEEV PERIODIC LAW:

⇒ He was unable to locate hydrogen in the periodic table.

⇒ Increase in atomic mass was not regular while moving from one element to another. Hence, the number of elements yet to be discovered was not predictable.

⇒ Later on, isotopes of elements were found which violated Mendeleev’s periodic law.

Answer 2

1. It does not tells us about tarnishing elements

2. It does not make a separate group for noble gases

3. Position cobalt and nickel does not justify

4. He does not able to set position of hydrogen in periodic table
5. It does not able to set isotopes in his periodic table