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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
1. Elements are arranged in the increasing order of their atomic masses. 1. Elements are arranged in the increasing order of their atomic numbers.
2. There are 8 groups 2. There are 18 groups
3. Each groups are subdivided into sub group 'a' and 'b' 3. Groups are not subdivided into subgroups.
4. Groups for Noble gas was not present as noble gases were not discovered by that time 4. A separate group is meant for noble gases.
5. There was no place for isotopes. 5. This problem has been rectified as slots are determined according to atomic number.

 

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