Atomic energy is the energy released during nuclear reactions, particularly through processes like fission and fusion. In fission, the nucleus of an atom, such as uranium or plutonium, splits into smaller parts, releasing a significant amount of energy. Fusion, on the other hand, occurs when two light atomic nuclei, like those of hydrogen, combine to form a heavier nucleus, also releasing energy. This energy can be harnessed for various applications, most notably in nuclear power plants to generate electricity. Atomic energy is also used in medical treatments, such as radiation therapy, and in scientific research, including particle physics experiments.