Question

drawbacks of medeleev table​

Answer 1

Demerits of Mendeleev Periodic Table :

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.

Pls mark me as brainliest because I gave speed answer.....

Answer 2

Drawbacks:-

• Position of hydrogen is uncertain.
• As hydrogen has properties similar to both first and 7 group elements, therefore position of hydrogen is not fixed or appropriate.

It has been placed in IA and VIIA groups because of its resemblance with both groups.

• No separate groups for isotopes. As at that time there was not any role of isotopes so mendeleev doesn't specify a space for isotopes of the elements.
• No separate group for lanthanides and actinides
• Also there is no resemblance expect valency of sub groups A and B they have been put in the same groups. Some of the elements were placed together whose properties were not similar to each other and some elements were such that their properties were similar but wasn't put together.
• The order of increasing atomic weights is not strictly followed in the arrangement of elements in periodic table.

For eg : Argon having mass of 39.9 was placed before Potassium having weight of 39.1.

Cobalt having mass of 58.9 was placed before Nickel having weigh of 58.6.

Tellurium having mass of 127.6 was placed before Iodine having weigh of 126.9.