Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and the Modern Periodic Table.
Mendeleev’s Periodic Table
Elements are arranged in the increasing order of their atomic masses.
There are 8 groups
Each groups are subdivided into sub group ‘a’ and ‘b’
Groups for Noble gas was not present as noble gases were not discovered by that time
There was no place for isotopes.
Modern Periodic Table
Elements are arranged in the increasing order of their atomic numbers.
There are 18 groups
Groups are not subdivided into sub-groups.
A separate group is meant for noble gases.
This problem has been rectified as slots are determined according to atomic number.