Question

STATEMENT - 1 : ${}_Z{X}^A$ undergoes 2 $\alpha$ decays, 2$\beta$ decays (negative $\beta$) and 2 decays. As a result the daughter product is
${}_{Z-2}{Y}^{A-8}.$
STATEMENT -2 : In $\alpha$ decay the mass number decreases by 4 unit and atomic number decreases by 2 unit. In $\beta$ decay (negative $\beta$) the mass number remains unchanged and atomic number increases by 1 unit. In $\gamma$ decay, mass number and atomic number remains unchanged.

• A. Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1
• B. Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1
• C. Statement-1 is True, Statement-2 is False
• D. Statement-1 is False, Statement-2 is True.

Answer 1

Answer: (A)

Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1

In $\alpha$ decay, ${}_2^{4}He$ is released. Hence the atomic mass becomes $A-\left(2\right)\left(4\right)=A-8$ and atomic number becomes $Z-\left(2\right)\left(2\right)=Z-4$.

Then in $\beta$ decay, ${}_{-1}^{0}e$ is released. Atomic mass becomes $(A-8)+\left(2\right)\left(0\right)=A-8$ and atomic number becomes $(Z-4)+\left(2\right)\left(1\right)=Z-2$.

In $\gamma$ decay, atomic mas and atomic number remain unchanged.