Question

What is/are the drawback(s) of Mendeleev's periodic table?

• A. Placing of $H$ was not decided
• B. Gaps for new elements were left
• C. Position of isotopes were not defined
• D. Both (a) and (c)

Answer 1

The correct option is D Both (a) and (c)

Hydrogen resembles both, the alkali metals (IA) and the halogens (VIIA) in properties. So, Mendeleev could not decide where to place it.
As atomic mass of isotopes differs, they should have placed in different position in Mendeleev’s periodic table. However, there were no such places for isotopes in Mendeleev’s table.
Hence, these were the limitations of Mendeleev's peiodic table.