vodík

Vodík, with the chemical symbol H and atomic number 1, is the lightest element. It is the most abundant element in the universe by mass, found mainly in stars and gas clouds. On Earth, hydrogen exists mostly in compounds such as water and hydrocarbons; free hydrogen gas is comparatively rare.

Under standard conditions, hydrogen is a diatomic molecule (H2), a colorless, odorless gas with very low density. It is highly flammable and forms explosive mixtures with air at certain concentrations. Hydrogen is a strong reducing agent used in various chemical processes.

Hydrogen has three natural isotopes: protium (1H), deuterium (2H), and tritium (3H). Protium is the most abundant; deuterium occurs in natural water as heavy water (D2O) and is used in science and industry; tritium is radioactive and produced in reactors for specialized applications.

Production methods include steam methane reforming and electrolysis of water, with other routes such as coal gasification and biomass gasification. Major uses include ammonia synthesis (Haber-Bosch), refining, hydrogenation, and as an energy carrier in fuel cells and rocket propulsion.

Storage and safety: hydrogen is stored as compressed gas or cryogenic liquid (liquid hydrogen at about 20 kelvin). It requires compatible materials to avoid embrittlement. Leaks are hard to detect and can form explosive mixtures with air. Combustion produces only water, but emissions depend on the production method.

History: hydrogen was first described by Henry Cavendish in 1766 as a component of water. The name derives from the Greek hydor, "water-former". The Czech common name is Vodík.