What is the basic difference in approach between mendeleev's periodic law & the modern periodic law?

Explanation

Accoridng to Mendeleev's periodic law, physical and chemical properties of elements are a periodic function of their atomic weights. On the other hand, modernn periodic table states that physical and chemical properties of the elements are a periodic function of their atomic numbers. thus the basic difference in approach between medeleev's periodic law and modernn periodic law is the change in the basis of classification of elements from atomic weight to atomic number.