Mendeleev's Periodic Table

• When Mendeleev started his work, 63 elements were known. He examined the relationship between the atomic masses of the elements and their physical and chemical properties. 
• Among chemical properties, Mendeleev concentrated on the compounds formed by elements with oxygen and hydrogen. 
• He selected hydrogen and oxygen as they are very reactive and formed compounds with most elements. 
• The formulae of the hydrides and oxides formed by an element were treated as one of the basic properties of an element for its classification.

Mendeleev’s Periodic Table contains vertical columns called ‘groups’
and horizontal rows called ‘periods’

Achievements of Mendeleev’s Periodic table:

Achievements of Mendeleev’s Periodic table are as follows;

(i) There could be possible to classify all elements.

(ii) He prepared this periodic table on the basis of atomic masses of the elements.

(iii) Mendeleev left some gaps in his periodic table which was filled later.

(iv) When the noble gases were discovered, they could be placed in a new group without disturbing the existing order.

The periodic law of Mendeleev's Periodic table.

The physical and chemical properties of elements are the periodic function of their atomic masses in Mendeleev's Periodic table.

Limitations of Mendeleev’s Classification:

(i) No fixed position can be given to hydrogen in the Periodic
Mendeleev's Table.

(ii) There are no any place for isotopes. 

(iii) It was not possible to predict how many elements could be discovered between two elements.