The central part of an atom is called the "nucleus." The nucleus contains protons and neutrons and is responsible for most of the atom's mass. Protons, which carry a positive charge, determine the element's identity, while neutrons, which have no charge, contribute to the stability of the nucleus. The electrons, which have a negative charge, orbit around the nucleus, balancing the overall electrical charge of the atom. The behavior of the nucleus is fundamental to understanding atomic interactions, stability, and nuclear reactions, playing a critical role in fields like chemistry and physics.