(a) State the periodic law on which Mendeleev’s periodic table was based. Why and how was this periodic law changed ?(b) Explain why, the noble gases are placed in a separate group.

(a) According to Mendeleev’s periodic law, the properties of elements are a periodic function of their atomic masses. After was the discovery of atomic numbers,  Mendeleev’s periodic law was changed, which was based on atomic mass to atomic number.

(b) Noble gases (having completely filled outermost electron shells) are chemically inert or unreactive elements so they were placed in a different group.


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Updated on: 10-Oct-2022


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