Question

${}_{90}T{h}^{234}$ disintegrates to give ${}_{82}P{b}^{206}$ as the final product. How many $\alpha$ and $\beta -particles$ are emitted out during this process?

Answer 1

$\begin{array}{c}{}_{90}^{234}Th\\ Parent\end{array}⟶\begin{array}{c}{}_{82}^{206}Pb\\ Endproduct\end{array}$
Decrease in mass $=(234-206)=28$
Mass of $\alpha$-particle $=4$
So, Number of $\alpha$-particles emitted $=\frac{28}{4}=7$
Number of $\beta$-particles emitted $=2\times$ Number of $\alpha$-particles $-$ (Atomic number of parent $-$ Atomic number of end product)
$=2\times 7-(90-82)=6$