What role does the nucleus of an atom play?

The nucleus of an atom plays a crucial role in determining both the mass and stability of the atom. It is composed of protons and neutrons, collectively known as nucleons. The protons carry a positive charge, while neutrons are neutral, meaning they do not have any charge. Since these nucleons are densely packed together, they account for the majority of an atom's mass. Electrons, on the other hand, are located in orbitals surrounding the nucleus and contribute very little to the overall mass of the atom.

Understanding the makeup of the nucleus is fundamental in explaining atomic behavior. For example, the number of protons in the nucleus defines the element (its atomic number), while the number of neutrons can influence the isotope of that element. This fundamental structure is what underlies many chemical reactions and properties of elements.

The other choices do not accurately describe the nucleus's role in an atom. For instance, while it is true that the nucleus contains protons and neutrons, it does not contain only protons. Electrons do not reside within the nucleus but instead orbit it at varying distances, which directly contradicts another option. Additionally, while atoms do maintain charge balance, this is primarily due to the relationship between protons and