Hydrogen

Hydrogen is a nonmetal and the lightest element. It is also the most abundant element in the universe; nuclear fusion of hydrogen powers the Sun. At room temperature, hydrogen is a colorless, odorless, flammable gas made of molecules containing two atoms. On Earth, it occurs mainly combined with other elements in water and organic compounds. Industry obtains most hydrogen from fossil fuels, especially by reacting natural gas with steam. Electricity can also split water into hydrogen and oxygen, a process called electrolysis. Hydrogen is used to make ammonia for fertilizers and to process petroleum. In fuel cells, it reacts with oxygen to generate electricity and water.