Question

drawbacks of mendeleev ​

Answer 1

Answer:

Draw back of Mendeleev's periodic table:

• position of hydrogen, hydrogen is placed in group...
• Anomalous pairs: In certain pairs of elements, the increasing order of atomic masses was not obeyed.
• Position of isotopes: Isotopes are the atoms of the same element having different atomic masses but same atomic numbers.

Answer 2

Mendeleesv's periodic law:

It states that the physical and chemical properties of elements are periodic function of their atomic weight.

Drawbacks of Mendellev's periodic table:

• Unlike elements were placed in same group. Cu, Ag and Au were placed in group I with Na, K etc. though they differ in their properties.

• It was not clear that lanthenides and actenides were in IIIA or in IIIB group.

• Position of Hydrogen wasn't clear. As hydrogen resembles both alkali metals and the halogens Mendellev couldn't decide the place of Hydrogen in periodic table.

• As atomic weight is the fundamental of Mendellev's periodic table thus the position of isotopes of same elements would have been different. But there was no such arrangement in Mendellev's periodic table.

• Anomalous pairs are those which didn't follow the increasing order of atomic weight. Example : Ar is placed before K in periodic table but atomic weight of Ar > Atomic weight of K. (Ar = 39.9 amu and K= 39.1 amu)

• Similar elements were placed in different groups like Platinum and Gold were placed in VIII and IB respectively though they have similar properties.