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Compare and contrast the arrangement of elements in Mendeleev's Periodic Table and the Modern Periodic Table.

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Mendeleev's periodic table Modern periodic table
Elements are arranged in the increasing order of their atomic masses. Elements are arranged in the increasing order of their atomic numbers.
There are 8 Groups. There are 18 Groups.
Each group are subdivided into subgroup 'a' and 'b'

Groups are not subdivided into sub-groups.

Groups for Noble gas was not present as noble gases were not discovered by that time.

A separate group is meant for noble gases.

There was no place for isotopes.

This problem has been rectified as slots are determined according to atomic number.

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