Question

why there is no mention of noble gases like Helium neon and Argon in Mendeleev periodic table.

Answer 1

There was no mention of noble gases like helium, neon and argon as they were not known at that time and were discovered much later. Since they are very inert gases, it was difficult to discover them with the primitive technology.

Answer 2

The entire column of noble gases through could be missed because it was a periodic gap, not a gap in the period
medeleev added the noble gases later ,near the end of his life when sufficient evidence was collected
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