What type of nuclear reaction is characterized by low atomic number nuclei fusing to form a heavier nucleus?

Nuclear fusion is the process in which two light atomic nuclei combine to form a heavier nucleus, releasing a significant amount of energy in the process. This reaction typically occurs in stars, where hydrogen nuclei fuse to create helium under extreme temperature and pressure conditions.

The key aspect of nuclear fusion is that it involves low atomic number elements, such as hydrogen isotopes, fusing together. This mechanism is fundamental to stellar processes and is responsible for the energy produced in the sun and other stars, enabling them to shine for billions of years.

Understanding this concept is important because it distinguishes fusion from other nuclear processes, such as fission, where a heavy nucleus splits into lighter nuclei, or radioactive decay, which involves the transformation of unstable atomic nuclei into more stable ones, often emitting particles or radiation. Additionally, while a chain reaction refers to a series of fission events, fusion's primary focus remains on combining lighter nuclei into a heavier one.