Q. In his periodic table, Mendeleev could not assign a correct position to:
Answer: Hydrogen
Notes: The biggest limitation of Mendeleev’s Periodic Table was that Mendeleev could not assign a correct position of hydrogen in his periodic table, as the properties of hydrogen resembles both with alkali metals as well as with halogens. Besides, the isotopes of the same element will be given different position if atomic number is taken as basis, which will disturb the symmetry of the periodic table.