Nuclear Physics And Radioactivity Question 391

Question: $ _{90}^{232}Th $ an isotope of thorium decays in ten stages emitting six a-particles and four b-particles in all. The end product of the decay is [CPMT 2005]

Options:

A) $ _{82}^{206}Pb $

B) $ _{82}^{209}Pb $

C) $ _{82}^{208}Pb $

D) $ _{83}^{209}Br $

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Answer:

Correct Answer: C

Solution:

New mass number $ {A}’=A-4{n_{\alpha }} $ $ =232-4\times 6=208 $ atomic number $ {Z}’=Z+{n_{\beta }}-2{n_{\alpha }} $ $ =90+4-2\times 6=82 $