Nuclear structures refer to the organization and arrangement of protons and neutrons within an atomic nucleus. These particles are held together by the strong nuclear force, which is one of the four fundamental forces of nature. The number of protons determines the element, while the total number of protons and neutrons defines the isotope of that element. The stability of nuclear structures can vary, leading to phenomena such as radioactive decay. Some nuclei are stable, while others are unstable and may emit radiation as they transform into more stable forms. Understanding nuclear structures is essential in fields like nuclear physics and nuclear energy.