Question

Assertion On a decay daughter nucleus shifts two places to the left from the parent nucleus.
Reason An alpha particle carries four units of mass.

• A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion
• B. If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion
• C. If Assertion is true but Reason is false
• D. If both Assertion and Reason are false

Answer 1

Answer: (B)

We know that on $\alpha$-particle carries $2$ units of positive charge and four unit of mass. On $\alpha$-decays, charge number of parent nucleus decreases by $2$ units. As classification or grouping of elements is based on charge number, hence daughter nucleus shifts two places to the left from the parent nucleus.