Question

The number of $\alpha$ and $\beta$ particles emitted during the transformation of ${}_{90}T{h}^{232}$ to ${}_{82}P{b}^{208}$ are respectively :

• A. 4, 2
• B. 2, 2
• C. 8, 6
• D. 6, 4

Answer 1

The correct option is D 6, 4

Number of alpha particles lost $=\frac{232-208}{4}=\frac{24}{6}=6$
Number of beta particles lost $=82-90+2\left(6\right)=-8+12=4$
Hence, 6 alpha and 4 beta particles are lost.
Note: When an alpha particle is lost, the atomic number decreases by 2 and the mass number decreases by 4.
When a beta particle is lost, the atomic number increases by 1.