Question

iv) What was the impact of the discovery of

Noble gases on Mendeleev's periodic
classification of elements?​

Answer 1

Mendeleev's periodic law: The properties of elements are a periodic function of their atomic masses. It was the discovery of atomic numbers which led to a change in Mendeleev's periodic law which was based on atomic mass.The elements having similar chemical properties from oxides and hydrides having similar formulae. Mendeleev used these properties for creating his periodic table.Limitations of Mendeleev's classification of elements. (i) The position of isotopes could not be explained. (ii) Wrong order of atomic masses of some elements could not be explained. (iii) A correct position could not be assigned to Hydrogen in the periodic table.Scandium and Germanium are two other elements that have since been discovered for which Mendeleev had left gaps in his periodic table.Noble gases group were missing from Mendeleev's original periodic table.