Question

Assertion (X): Mendeleev placed Co before Ni in the periodic table by violating the trend of increasing atomic mass

Reason (Y): The sequence was inverted to group the elements with similar properties together

• A. Both X and Y are true and Y is the correct explanation of X
• B. Both X and Y are true and Y is not the correct explanation of X
• C. X is true, Y is false
• D. Both X and Y are false

Answer 1

The correct option is A Both X and Y are true and Y is the correct explanation of X

Mendeleev grouped certain elements with similar properties together, eventhough the sequence of increasing atomic mass got abrupt because of it.

For example, Co was placed before Ni in his periodic table