Compare and contrast the arrangement of elements in Mendeleev’s Periodic Table and the Modern Period

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

Solution:

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.