Write few important postulates of Mendeleev periodic table mention in few limitation
Answers
Answer: features
periodic law: the properties of elements are a periodic function of their atomic masses
Mendeleev arranged elements on the basis of a fundamental property of atomic masses and also based on their chemical properties
elements are arranged in vertical columns known as groups and horizontal rows known as rows
periodicity / recurring of elements of similar properties is observed in this table
also Mendeleev arranged elements on the types of hydrides and oxides they form, which is the reason for the periodicity observed
limitations
the controversial position of hydrogen - hydrogen can behave both as an alkali metal and as a halogen , due to which it can have no specific position in the table . but in this table it is placed along with the alkali metals
hydrogen has one valence electron, same as the other alkali metals like sodium but also can form covalent bonds with metals and non metals and form diatomic molecule as well
the wrong order of atomic masses- some elements such as cobalt and nickel have been arranged wrongly in the periodic table .
the position of isotopes cannot be explained in this table
prediction of elements between heavy metals became difficult due to the fact that atomic masses do not increase in a particular pattern or manner