Question

Why were noble gas not a part of mendeleev periodic table in the beginning?

Answer 1

noble gas was not a part of mendeleev's period table because at that time the noble gas was not discovered as it was present in low concentration in atmosphere

Answer 2

The noble gasses were not mentioned in Mendeleev periodic table because when he made the table the noble gasses were not found but after they were found he made place for it without disturbing any element in the table