Question

Which of the following is not correct about Mendeleev's periodic table?

• A. The position of hydrogen in the periodic table was uncertain
• B. It helped in correcting the doubtful masses of some elements including beryllium
• C. The isotopes were assigned specific places in the table
• D. Noble gases once discovered could be placed separately without disturbing the existing order

Answer 1

The correct option is C The isotopes were assigned specific places in the table

Isotopes of an element have the same atomic number but a different mass number.

Mendeleev could not explain the position of isotopes in his periodic table and hence, their postions were uncertain.