Question

In a radioactive decay chain, $^{232}_{90}Th$ nucleus decays to $^{212}_{92}Pb$ nucleus. Let $N_{\alpha}$ and $N_{\beta}$ be the number of $alpha$ and $\beta^{-}$ particles, respectively, emitted in this decay process. Which of the following statements is (are) true?

• A. $N_{\alpha} = 5$
• B. $N_{\alpha} = 6$
• C. $N_{\beta} = 2$
• D. $N_{\beta} = 4$

Answer 1

Answer: (C)

$N_{\beta} = 2$

Answer 2

$^{232}_{90}Th$ Th is converting into $^{212}_{82}Pb$
Change in mass number (A) = 20
$\therefore$ no of $\alpha$ particle $= \frac{20}{4} = 5$
Due to $5 \, \alpha$ particle, z will change by 10 unit.
Since given change is 8, therefore no. of $\beta$ particle is 2