Question

what is the difference between Medeleev and Moder periodic table

Answer 1

In Mendleeve's periodic law elements were arranged on the basis of increasing atomic mass .
In Modern periodic law elements were arranged on the basis of increasing atomic number .

Answer 2

The major difference is that the elements in Mendeleev’s periodic table were arranged by atomic mass and the modern periodic table arranges elements by atomic number. Of course as elements are constantly being discovered there were significantly fewer elements in Mendeleev’s periodic table.