Question

What are the defect of Mandeleef's periodic table

Answer 1

heya @user
here is your answer
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Defects of Mandeleef's Periodic Table are following ::-

1. position of hydrogen :- hydrogen disamble alkali metal and hydrogen is its property. Hence its position was not sure.

2. position of isotopes :- the isotopes have different atomic weight and the periodic table is based on atomic weights. therefore isotopes should get different place in the periodic table on the basis of atomic number.

3. it is not proper to place together that element having different properties such as coinage metal ( Cu, Ag and Au ) with alkali metals, Zn, Cd and Hg with alkaline earth metal and like Mn with halogen. similarly Pt and Au having similar properties have been placed in different groups

4. lot of a stress was given to balance of elements.

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Hope helped !!

Answer 2

heya

In some cases Mendeleev placed elements according to their similarities in properties and not in increasing order of their atomic masses. Thus, the position of these elements was not justified e.g. cobalt (atomic mass 58.9) was placed before nickel

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