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:

Isotones are nuclei with the same number of neutrons ($N = A - Z$). For $_{34}Se^{74}$, $N = 74 - 34 = 40$. For $_{31}Ga^{71}$, $N = 71 - 31 = 40$. Since both have 40 neutrons, they are isotones.