Hydrogen is a chemical element with symbol H and atomic number 1. With an average atomic weight of 1.00794 u (1.007825 u for hydrogen-1), hydrogen is the lightest element and its monatomic form (H1) is the most abundant chemical substance, constituting roughly 75% of the Universe's baryonic mass. Non-remnant stars are mainly composed of hydrogen in its plasma state.
At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H2. Naturally occurring atomic hydrogen is rare on Earth because hydrogen readily forms covalent compounds with most elements and is present in the water molecule and in most organic compounds. Hydrogen plays a particularly important role in acid-base chemistry with many reactions exchanging protons between soluble molecules.
In ionic compounds, it can take a negative charge (an anion known as a hydride and written as H−), or as a positively charged species H+. The latter cation is written as though composed of a bare proton, but in reality, hydrogen cations in ionic compounds always occur as more complex species.
The most common isotope of hydrogen is protium (name rarely used, symbol 1H) with a single proton and no neutrons. As the simplest atom known, the hydrogen atom has been of theoretical use. For example, as the only neutral atom with an analytic solution to the Schrödinger equation, the study of the energetics and bonding of the hydrogen atom played a key role in the development of quantum mechanics.
Hydrogen gas was first artificially produced in the early 16th century, via the mixing of metals with strong acids. In 1766–81, Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance, and that it produces water when burned, a property which later gave it its name: in Greek, hydrogen means "water-former".
Industrial production is mainly from the steam reforming of natural gas, and less often from more energy-intensive hydrogen production methods like the electrolysis of water. Most hydrogen is employed near its production site, with the two largest uses being fossil fuel processing (e.g., hydrocracking) and ammonia production, mostly for the fertilizer market.
Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks.
Other articles related to "hydrogen":
... The atomic hydrogen torch uses it to generate very high temperatures near 4,000°C for welding ... Hydrogen is a powerful reducing agent which eliminates the need for flux to prevent oxidation of the weld ... Atomic hydrogen determines the frequency of hydrogen masers which are used as precise frequency standards ...
... Hydrogen poses a number of hazards to human safety, from potential detonations and fires when mixed with air to being an asphyxiant in its pure, oxygen-free form ... In addition, liquid hydrogen is a cryogen and presents dangers (such as frostbite) associated with very cold liquids ... Hydrogen dissolves in many metals, and, in addition to leaking out, may have adverse effects on them, such as hydrogen embrittlement, leading to cracks and explosions ...
... In France during 1783, the first public experiment with hydrogen-filled balloons involved Jacques Charles, a French professor of Physics and the Robert brothers, renowned ... Charles provided large quantities of hydrogen, which had only been produced in small quantities previously, by mixing 540 kg of iron and 270 kg of sulfuric acid ...
... Atomic hydrogen (or nascent hydrogen) consists of individual hydrogen atoms that are not bound together like those in ordinary hydrogen molecules ... species is denoted by H (atomic), contrasted with the usual H2 (dihydrogen or just 'hydrogen') commonly involved in chemical reactions ... According to one claim, nascent hydrogen is generated in situ usually by the reaction of zinc with an acid, aluminium (Devarda's alloy) with sodium hydroxide, or by electrolysis at the cathode ...
... Organisations who officially endorse the Hydrogen Expedition Bluewater Network National Hydrogen Association of Australia Save the Planet USA Environment Colorado Italian Hydrogen and Fuel Cell Association ...
Famous quotes containing the word hydrogen:
“All you of Earth are idiots!... First was your firecracker, a harmless explosive. Then your hand grenade. They begin to kill your own people a few at a time. Then the bomb. Then a larger bomb, many people are killed at one time. Then your scientists stumbled upon the atom bombsplit the atom. Then the hydrogen bomb, where you actually explode the air itself.”
—Edward D. Wood, Jr. (19221978)
“The pace of science forces the pace of technique. Theoretical physics forces atomic energy on us; the successful production of the fission bomb forces upon us the manufacture of the hydrogen bomb. We do not choose our problems, we do not choose our products; we are pushed, we are forcedby what? By a system which has no purpose and goal transcending it, and which makes man its appendix.”
—Erich Fromm (19001980)