Question

Assertion (A) Mendeleev's arranged elements in horizontal rows and vertical columns.
Reason (R) Mendeleev's ignored the order of atomic weight thinking that the atomic measurements might be incorrect.

• A. Both $A$ and $R$ are correct; $R$ is the correct explanation of $A$.
• B. Both $A$ and $R$ are correct; and $R$ is not the correct explanation of $A$.
• C. $A$ is correct; $R$ is incorrect.
• D. $R$ is correct; $A$ is incorrect.

Answer 1

Answer: (B)

(b) Mendeleev's arranged elements in horizontal rows and vertical columns in order of their increasing atomic weights in such a way that, the elements with similar properties occupied the same vertical column or group. Thus, both $A$ and $R$ are correct but $R$ is not the correct explanation of $A$.