Atomic (nuclear) refers to the energy and processes associated with the nucleus of an atom, which is the central part of an atom containing protons and neutrons. This energy can be released through nuclear reactions, such as fission, where the nucleus of an atom splits into smaller parts, or fusion, where two nuclei combine to form a heavier nucleus. These processes are fundamental to the functioning of nuclear power plants and the development of nuclear weapons. The study of atomic (nuclear) physics has led to significant advancements in various fields, including medicine, where techniques like nuclear imaging and radiation therapy are used for diagnosis and treatment. Additionally, understanding atomic interactions is crucial for research in particle physics and the development of new materials.