Question

A nucleus ${}_n^{m}X$ emits one $\alpha$ particle and two $\beta$ particles. The resulting nucleus is

• A. ${}_{n-4}^{m-6}Z$
• B. ${}_n^{m-6}Z$
• C. ${}_n^{m-4}Z$
• D. ${}_{n-2}^{m-4}Z$

Answer 1

Answer: (C)

${}_n^{m-4}Z$

In alpha decay, decreases 4 unit mass number and 2 unit atomic number.

In beta decay, increases one unit atomic number but mass will remain same.

So, ${}_n^{m}X{\to }^{\alpha }$ ${}_{n-2}^{m-4}Y{\to }^{2\beta }$ ${}_{n-2+2}^{m-4}Z$ or ${}_n^{m-4}Z$