Nucleus: Practice Problem & Solution

Solution Explained:

To solve this problem, we apply the core principles of Nucleus. Understanding the underlying formula is key to arriving at the correct answer below:

Emission of an $\alpha$ particle reduces mass number by 4 and atomic number by 2 (result: $^{m-4}_{n-2}X'$). Emission of two $\beta^-$ particles increases atomic number by 2 while leaving mass number unchanged (result: $^{m-4}_{n-2+2}Z = ^{m-4}_{n}Z$).