Limitations Of Mendeleev’s Periodic Table

Mendeleev’s Periodic Table in spite of its advantages suffers from the following drawbacks and has thus limitations in its application:

Position of hydrogen is not clear because it resembles with both alkali metals and halogens. It gives the positive H+ ions like alkali metals and gives the hydride ions like halides.

Certain chemically similar elements, e.g., copper, gold, platinum are placed in different groups while some dissimilar elements are grouped together.

Certain elements of higher atomic weight precede others with lower atomic weight. Argon (At. Wt. = 40) Precedes Potassium (At. Wt. = 39) Cobalt (At. Wt. = 59) Precedes Nickel (At. Wt. = 58.6)

No position is assigned to isotopes in different groups.

Maximum valence state is depicted by an element in a particular group. The elements of group VIII usually do not depict 8 maximum oxidation state except ruthenium and osmium.

No explanation is available for the inert pair effect and stability of valence states differing by units of two.