The radioactive disintegration series begins with Uranium-238 () and eventually terminates at the st — Nuclear Chemistry and Radioactivity Chemistry Question

💡 Solution & Explanation

Total change in mass number $\Delta A = 238 - 206 = 32$. Since only $\alpha$ -particles change mass (by 4), the number of $\alpha$ -particles = $32 / 4 = 8$. Each $\alpha$ -emission reduces $Z$ by 2. Total expected decrease in $Z = 8 \times 2 = 16$. Thus, expected $Z$ without $\beta$ emissions = $92 - 16 = 76$. The actual final $Z$ is 82. The difference is $82 - 76 = 6$. Since each $\beta^-$ -emission increases $Z$ by 1, there must be exactly 6 $\beta^-$ -particles emitted.