Question

Explain any two defects of Mendeleev's periodic table which were overcome in modern periodic table

Answer 1

1 position of hydrogen was not confirmed
2 element with a slightly higher atomic mass was placed before an element of lower atomic mass.
These defects were overcome in the modern periodic table

Answer 2

position of hydrogen
hydrogen is not given a fixed position.it is considered as group 1A as well as in group 7A element.
Electronic arrangement
It doesn't explain the electronic arrangement of elements.
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