Question

limitations of mandeleev's periodic table

Answer 1

The atomic masses of elements did not increase in a steady manner while going from one element to other which made it difficult to predict the number of elements that could be discovered between two elements.

Answer 2

There were almost three limitations of MENDELEEV'S periodic table;-
1.There was no such fixed position for H (hydrogen)
2. As, isotopes were introduced long after his periodic table was introduced 
so............isotopes made a challenge to Mendeleev's periodic table.
3. Atomic mass doesn't increase in a regular manner.