CBSE Class 11-science Answered

The main draw backs of the Mendeleev's periodic table are as follows:
i) The position of hydrogen in the periodic table was not certain, it was placed in first as well as eighth group.
ii) Some elements of higher atomic weight were placed before the elements with lower atomic weight.
iii) Lanthanides and actinides were not given a proper position.
iv) Isotopes of elements were placed in the same position in the table.
v) The noble gases were not given any space in the periodic table.
vi) Some chemically similar elements were placed in different groups and some dissimilar elements were placed in the same group.