The atomic nucleus is the central part of an atom, containing protons and neutrons. Protons are positively charged particles, while neutrons have no charge. Together, they make up most of the atom's mass. The number of protons in the nucleus determines the element, such as hydrogen or oxygen, and is known as the atomic number. Surrounding the nucleus are electrons, which are negatively charged particles that orbit in specific energy levels. The balance between the number of protons and electrons gives the atom its overall charge. Understanding the atomic nucleus is essential for studying topics like nuclear energy, radioactivity, and chemical reactions.