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:

Mass number A is the sum of protons and neutrons, while atomic number Z is just the number of protons. For hydrogen ($^1H$), there are no neutrons, so A = Z. For all other stable nuclei, A > Z. Thus, it is sometimes equal.