Question

In Mendeleev's Periodic Table, why was there no mention of Noble gases like Helium, Neon and Argon?

Answer 1

As we know that there are 118 elements present in our periodic table out of which 94 elements are natural elements and 24 elements are synthetic elements. The tabular representation of all the elements altogether arranged according to their respective properties is known as periodic table.

Complete answer:
Let us discuss about the Mendeleev Periodic Table as follows:-
-Dmitri Ivanovich Mendeleev (a Russian chemist) was the most important contributor to the early development of the periodic table and was also known as father of the modern periodic table. Many periodic tables were introduced but the most important one was the Mendeleev periodic table.
-He arranged the elements on the basis of the fundamental property, atomic mass, and chemical properties. During his time period of work only 63 elements were known. After studying and observing the properties of every element, he formulated a periodic law which states:
“The properties of elements are the periodic function of their atomic masses.”
-In the Mendeleev periodic table, vertical columns were named as groups and horizontal rows were named as periods.
-There was no mention of noble gases like helium, neon, and argon in his table because they were not known at that time and were discovered much later. Also being very inert gases, it was difficult to detect them with the help of primitive technology present at that time.

Note:
-Merits of Mendeleev’s Periodic Table are that he left some gaps left for the elements yet to be discovered. Hence, if any new element was discovered, it could be easily placed in a new group without disturbing any existing group.
-Demerits of Mendeleev’s Periodic Table are that he was unable to locate the place of hydrogen and the discovery of isotopes violated the periodic rule stated by him.