Protium is the most common isotope of the element hydrogen, consisting of one proton and one electron, with no neutrons. It has an atomic number of 1 and an atomic mass of approximately 1 atomic mass unit (amu). Protium is a colorless, odorless gas at room temperature and is essential for various chemical reactions, including the formation of water when it combines with oxygen. In nature, protium makes up about 99.98% of all hydrogen found on Earth. It plays a crucial role in nuclear fusion processes in stars, including our Sun, where hydrogen nuclei fuse to form helium, releasing vast amounts of energy.