hidrogen

Hydrogen, sometimes written as hidrogen in some languages, is the chemical element with symbol H and atomic number 1. It is the lightest and most abundant element in the universe, making up about 75% of its normal baryonic mass. In the universe it is mainly found in stars and gas giant planets; on Earth it is mostly bound in water and organic compounds.

At standard conditions hydrogen exists as a diatomic molecule, H2. It is colorless, odorless, and tasteless. It has a very low atomic mass (1.008 u) and a boiling point of −252.87 °C; it becomes a gas well below room temperature. It is highly flammable and forms explosive mixtures with air at a range of concentrations.

Hydrogen occurs naturally in molecular form in trace amounts in the atmosphere, but is mainly produced industrially for use in chemical manufacturing and energy applications. The most common methods are steam methane reforming and water electrolysis; other methods include coal gasification and petrochemical processing. Hydrogen production varies in environmental footprint depending on energy source.

Hydrogen was first produced in a recognized form by Henry Cavendish in 1766, who described its properties as part of "inflammable air." It was later named hydrogen by Antoine Lavoisier in 1783 as the "water-former" (hydrogenium).

Major uses include ammonia synthesis for fertilizers, hydrocracking and refinery processes, and hydrogenation reactions in the chemical industry. It is also used in metal fabrication, glass production, and as a fuel in rockets and in emerging fuel-cell technologies for clean electricity generation and transportation.

Safety and storage considerations include its high flammability and tendency to form explosive mixtures with air. It is stored as compressed gas or as a cryogenic liquid (liquid hydrogen). It has several isotopes, including protium, deuterium, and tritium.