Which group of elements could be placed in Mendeleev's Periodic Table without disturbing the original order ? Give reason

CBSE Class 10 CBSE Class 10 Science
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Noble gases.
According to Mendeleev’s classification, the properties of elements are the periodic function of their atomic masses and there is a periodic recurrence of elements with similar physical and chemical properties. Noble gas being inert, could be placed in a separate group without disturbing the original order.