Question

What are the limitations of Mendeleev's periodic table? How could the modern periodic table overcome the limitations of Mendeleev table?

Answer 1

Limitations of Mendeleev.s periodic table :

• Elements with a large difference in properties were included in the same group. Eg: Hard metals like copper (Cu) and silver (Ag) were included along with soft metals like sodium (Na) and potassium (K).

• No proper position could be given to the element hydrogen. Non-metallic hydrogen was placed along with metals like lithium (Li), sodium (Na), and potassium (K).

• The increasing order of atomic mass was not strictly followed throughout. For example in cobalt and nickel & Tellurium and Indium.

• No place for isotopes in the periodic table.

The Modern Periodic Table could remove various anomalies of Mendeleev’s Periodic Table:

a) In the Modern Periodic table elements are arranged in the increasing order of their atomic number, removing the anomaly regarding certain pairs of elements in Mendeleev’s periodic table.

b) The Atomic number of cobalt is 27and nickel is 28. Hence cobalt will come before nickel even though its atomic mass is greater.

c) All isotopes of the same elements have different atomic masses, but the same atomic number; therefore they are placed in the same position in the modern periodic table.