State 3 limitations of Mendeleeve's Periodic Table

Limitations are : Position of hydrogen : Hydrogen is placed in Group IA. However, it actually resembles the elements of Group-IA (alkali metals ) as well as the elements of Group VII-A (halogens ). Thus, the position of hydrogen in the periodic table is not clear. Position of isotopes : On the basis of atomic weight , various isotopes of the same elements should be assigned different places in the periodic table. Mendeleev could not provide separate places for isotopes. Position of lanthanides and actinides : Fourteen elements following Lanthanum(known as lanthanides orrare earths) and the fourteen elements following Actinium (known as actinides or transuranic elements ) have not been provided separate and proper places in the Mendellev 's table, rather they have been placed in two rows at the bottom of the table.