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Question: Answered & Verified by Expert
${ }_{90} \mathrm{Th}^{228}$ emits four alpha and one beta particles. Number of neutrons in daughter element is
ChemistryChemical KineticsMHT CETMHT CET 2011
Options:
  • A 129
  • B 190
  • C 232
  • D 138
Solution:
1229 Upvotes Verified Answer
The correct answer is: 129
$90 \mathrm{Th}^{228} \underset{-4 \alpha}{\longrightarrow} 82^{212} \underset{-\beta}{\longrightarrow}{ }_{83} \mathrm{Y}^{212}$
daughter element
Number of neutrons = mass number - atomic number
$$
\begin{array}{l}
=212-83 \\
=129
\end{array}
$$

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