Question

Compare and contrast the arrangement of elements in Mendeleev's periodic table and the Modern periodic table.

Answer 1

Hint: To solve this question we have to check the correction that is made in the classification of the Modern Periodic Table which helps us to rectify the problem that arose in the Mendeleev's Periodic Table. In Mendeleev's periodic table there is no place for isotopes.

Complete step by step solution:
From your chemistry lessons you have learned about the Mendeleev's Periodic Table and its modification which is known as the Modern Periodic Table. Let us compare both of them in the tabular form.

Mendeleev's Periodic Table	Modern Periodic Table
Mendeleev's Periodic Table was discovered by Dmitri Mendeleev in 1869.	The Modern Periodic Table was discovered by Henry Moseley in 1913.
In Mendeleev's Periodic Table elements are arranged on the basis of their increasing atomic masses.	In Modern Periodic Table elements are arranged on the basis of their increasing atomic mass.
In this table there are 7 periods and 8 group	In this table there are 7 periods and 18 groups
Here each group is divided in the subgroups that are a and b.	Here no division of groups into subgroups takes place.
At that time noble gas was not discovered therefore the groups for noble gas were not present in the periodic table.	In the Modern Periodic Table a separate group for noble gas is present that is group 18.
In Mendeleev's Periodic Table there is no place for isotopes	As we know that the isotopes have the same atomic number therefore in the Modern Periodic Table there is no need for any separate location for the isotopes.
In Mendeleev's Periodic Table no special reason is given for the triad elements of group viii.	In the Modern Periodic Table no such special grouping is required.

Note: In Mendeleev's Periodic Table there is an arrangement of only 63 elements which were discovered at that time while in the Modern Periodic Table all the 118 natural as well as synthetic elements are accommodated. Modern Periodic Table is more acceptable because it is based on the atomic number and atomic number is used as much more fundamental property in distinguishing the elements and used as a better criteria for deciding the physical and chemical properties of elements.