The atomic nucleus is the small, dense region at the center of an atom that contains most of the atom's mass. It is composed of two types of subatomic particles: protons and neutrons. - **Protons** are positively charged particles, and their number determines the atomic number of an element, which defines the element itself (e.g., hydrogen has one proton, while carbon has six). - **Neutrons** are neutral particles, meaning they have no charge.
