Question

what are the limitations of mendeleef periodic table?​

Answer 1

Answer:

1.The russian scientist dmitri mendeleev developed the periodic table in the year 1869 to 1871 ad.

2.He arranged 63 elements known at that time.

3.Limitations are:He arranged the isotopes of same elements in the same boxes.

4.He arranged the elements on the basis of atomic mass which was later on taken to be right by atomic number given by moseley in modern periodic table.

5.Proper place for hydrogen could not be assigned in his table.

6.The whole number atomic mass of cobalt and nickle is same .Therefore their was an ambiguity regarding their right place.

7.Due to uncommon rise in atomic mass how many heavy elements could be there in between two heavy elements can be there can't be determined.

Answer 2

$\huge\textsf{Mendeleef's \: Periodic \: Table \: Limitations}$

• 1. Position of Hydrogen :-

Hydrogen resembles both , alkali metal and the halogen in properties so Mendeleev could not decide where to place it.

• 2. Position of isotopes :-

As atomic weight of isotopes differes, they should have placed in different position in Mendeleef's periodic table. But there were no such places for isotopes in Mendeleef's Table.

• 3. Anomalous pairs of elements :-

There were some pairs of elements which did not follow the increasing order of atomic weights.

Example :-

Ar and Co were placed before K and Ni in Periodic table , but having higher atomic weights .

• 4. Like elements were placed in different groups :-

There were some elements like Platinum (PT) and Gold (Au) which have similar properties but we're placed in different groups in Mendeleef's Table.

• 5. Unlike elements were placed in same group :-

Cu , Ag , Aur placed in first group along with Na, K etc . While they differ in their properties

• 6. It was not clear that lanthanide and Actinides are related with |||A group or |||B group.

• 7. Cause of periodicity :-

Why Physical and Chemical properties repeated in a group.