Limitations of Mendelev’s periodic table –
(a) Elements with large difference in properties were included in the same group.
Eg. Elard metals like copper (Cu) and silver (Ag) were included along with soft metals like sodium and potassium
(b) No proper position could be given to the element hydrogen. Non-metallic Hydrogen was placed along with metals like lithium, sodium and potassium.
(c) The increasing order of atomic mass was not strictly followed throughout.
Eg. – Co & Ni, te & I.
(d) No place for isotopes in the periodic table. The modem periodic table is an extension of the original Mendeleev’s periodic table and is known as the long form of periodic table. Mendeleev’s initial table had 63 elements, modem table has 109 elements. It is also known important to note how the modem periodic table is arranged.
Although the columns which reflect a natural order have been retained, the row’s of the modem table show elements in the order of Mendeleev’s columns. In other words the elements of what we now call ‘a period’ were listed vertically by Mendeleev. ‘Groups are now shown vertically in contrast to their horizontal format in Mendeleev’s table
