Question

Which of the following is drawback of Mendeleev’s periodic table :

• A. He arranged the known elements in the order of their increasing atomic masses
• B. He helped in predicting the discovery of new elements
• C. Iodine having lower atomic mass than Tellurium was placed ahead of Tellurium.
• D. None of the above

Answer 1

The correct option is C Iodine having lower atomic mass than Tellurium was placed ahead of Tellurium.

Mendeleev violated his periodic law at certain places to give appropriate positions to the few elements on the basis of their properties. Iodine (Atomic weight = $126.9$) having lower atomic mass than Tellurium (Atomic weight = $127.6$) was placed ahead of Tellurium because Iodine showed similar properties with Fluorine, Chlorine and Bromine.