The Total solution for NCERT class 6-12
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 groups are subdivided into sub group ‘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.