Question

The drawbacks of Mendeleev's Periodic Table are:

• A. Position of Hydrogen was unclear
• B. Position of Lanthanides and Actinides
• C. Position of Isotopes
• D. Anomalous positions of some elements

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A

Position of Hydrogen was unclear

B

Position of Lanthanides and Actinides

C

Position of Isotopes

D

Anomalous positions of some elements

Mendeleev's table had some major drawbacks:

(i) The position of Hydrogen- Hydrogen resembles the elements of both group 1 and group 7. So, its position was controversial in the table.

(ii) The position of isotopes- On the basis of atomic masses, different isotopes of the same element should be given different positions in the periodic table. But they were assigned a single position.

(iii) The position of Lanthanides and Actinides- Lanthanides and Actinides were placed at the bottom of the periodic table. They were not placed in the regular periodic table.