Question

Which of the following statements are correct about Mendeleev's periodic table?
i) It is based on increasing order of atomic numbers.
ii) Mendeleev corrected the atomic weight of some elements like Be, In etc.
iii) $(Ar,H_2),(Co,C{l}_2),(Te,F_2)$ are three inverted pairs.
iv) It is based on increasing order of atomic weights.

• A. only (i) correct
• B. (ii) and (iv) are correct
• C. only (iii) correct
• D. (i) and (iv) are correct

Answer 1

Answer: (B)

(ii) and (iv) are correct

Mendeleev's periodic table is based on the increasing order of atomic weights.
It follows the periodic law which states that the physical and chemical properties of elements are a periodic function of their atomic weights.
Hence, statement (i) is incorrect and (iv) is correct.
Mendeleev corrected the atomic weight of some elements like Be, In, Au, Pt, etc based on their position in the periodic table.
For example, the atomic mass of beryllium was corrected from $13.5$ to $9$. Hence, statement (ii) is correct.
The inverted pairs are ($Ar,K$), ($Co,Ni$) and ($Te$, $I_2$). They are also called anomalous pairs. Their positions are not justified.
Hence, the statement (iii) is incorrect.