In a radioactive decay chain, 90 232 Th nucleus decays to 82 212 Pb nucleus. Let N α and N β be the number of α and β - particles, respectively, emitted in this decay process. Which of the following statements is (are) true?

Physics · Nuclear Physics

JEE Advanced 2018 — Paper 2 — Question 4

In a radioactive decay chain, ${ }_{90}^{232} \mathrm{Th}$ nucleus decays to ${ }_{82}^{212} \mathrm{~Pb}$ 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?

Option A:
$\mathrm{N}_{\alpha}=5$
Correct
Option B:
$\mathrm{N}_{\alpha}=6$
Option C:
$\mathrm{N}_{\beta}=2$
Correct
Option D:
$\mathrm{N}_{\beta}=4$

Answer: A, C

Step-by-step solution

${ }_{90}^{232} \mathrm{Th} \longrightarrow{ }_{82}^{212} \mathrm{~Pb}+\mathrm{N}_{\alpha} \alpha+\mathrm{N}_{\beta} \beta$

No. of $\alpha=\frac{232-212}{4}=5$

No. of $\beta^{-}=2$ (from conservation of charge)

Answer key and solution verified before publishing.

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Exam: JEE Advanced 2018
Paper: Paper 2
Subject: Physics
Chapter: Nuclear Physics
Topic: Laws of Radioactive Decay