Question

Which of the following was one of the limitations of Mendeleev’s periodic table?
A.The discovery of the isotopes
B.The discovery of Noble gases
C.The discovery of metalloids
D.None of the above

Answer 1

Hint: Mendeleev arranged the elements in order of increasing relative atomic mass. When he did this, he noted that the chemical properties of the elements and their compounds showed a periodic trend.

Complete step by step answer:
-There are six periods (numbered from 1 to 6) or horizontal rows in the Mendeleev’s periodic table. The periods 4, 5 and 6 are divided into two halves.
-The discovery of isotopes was one of the limitations of Mendeleev’s periodic table.
-Since, Mendeleev’s periodic table was based on atomic masses of elements, so the isotopes should be placed in different columns despite the fact that they represent the same element and hence, isotopes haven’t been given a separate place in the periodic table.
-Mendeleev’s periodic table simplified the study of elements. As the arrangements of elements showing properties were classified into groups, it was very useful in studying and remembering the properties of a large number of elements in a systematic way.

Hence, option A is correct.

Note:
Mendeleev’s periodic table became widely accepted, primarily because he predicted the characteristics and placement of elements which were yet to be discovered. He left gaps in his table to place the elements not known at that time. By looking at the physical and chemical properties of the elements, next to a gap, he could also predict the properties of these undiscovered elements.