Q9 / 150 · MHT CET 2011 · Chemistry
${ }_{90} \mathrm{Th}^{228}$ emits four alpha and one beta particles. Number of neutrons in daughter element is
- Correct answerA129
- B190
- C232
- D138
Solution
$90 \mathrm{Th}^{228} \underset{-4 \alpha}{\longrightarrow} 82^{212} \underset{-\beta}{\longrightarrow}{ }_{83} \mathrm{Y}^{212}$
daughter element
Number of neutrons = mass number - atomic number
$$
\begin{array}{l}
=212-83 \\
=129
\end{array}
$$
Hence, the correct answer is option: 'A'.