- dinitrogen oxide
- dinitrogen pentoxide
- dinitrogen reductase
- dinitrogen tetroxide
- dinitrogen trioxide
- Italian: diazoto
- Italian: diazoto
Nitrogen () is a chemical element that has the symbol N and atomic number 7 and atomic weight 14.0067. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere.
Many industrially important compounds, such as ammonia, nitric acid, organic nitrates (propellants and explosives), and cyanides, contain nitrogen. The very strong bond in elemental nitrogen dominates nitrogen chemistry, causing difficulty for both organisms and industry in converting the into useful compounds, and releasing large amounts of energy when these compounds burn or decay back into nitrogen gas.
The element nitrogen was discovered by Daniel Rutherford. Nitrogen occurs in all living organisms — it is a constituent element of amino acids and thus of proteins, and of nucleic acids (DNA and RNA); resides in the chemical structure of almost all neurotransmitters; and is a defining component of alkaloids, biological molecules produced by many organisms.
PropertiesNitrogen is a nonmetal, with an electronegativity of 3.0. It has five electrons in its outer shell and is therefore trivalent in most compounds. The triple bond in molecular nitrogen () is one of the strongest in nature. The resulting difficulty of converting () into other compounds, and the ease (and associated high energy release) of converting nitrogen compounds into elemental , have dominated the role of nitrogen in both nature and human economic activities.
At atmospheric pressure molecular nitrogen condenses (liquifies) at 77 K (−195.8 °C) and freezes at 63 K (−210.0 °C) into the beta hexagonal close-packed crystal allotropic form. Below 35.4 K (−237.6 °C) nitrogen assumes the alpha cubic crystal allotropic form. Liquid nitrogen, a fluid resembling water, but with 80.8% of the density, is a common cryogen.
Unstable allotropes of nitrogen consisting of more than two nitrogen atoms have been produced in the laboratory, like and . Under extremely high pressures (1.1 million atm) and high temperatures (2000 K), as produced under diamond anvil conditions, nitrogen polymerizes into the single bonded diamond crystal structure, an allotrope nicknamed "nitrogen diamond."
OccurrenceNitrogen is the largest single constituent of the Earth's atmosphere (78.082% by volume of dry air, 75.3% by weight in dry air). It is created by fusion processes in stars, and is estimated to be the 7th most abundant chemical element by mass in the universe.
Molecular nitrogen and nitrogen compounds have been detected in interstellar space by astronomers using the Far Ultraviolet Spectroscopic Explorer. Molecular nitrogen is a major constituent of the Saturnian moon Titan's thick atmosphere, and occurs in trace amounts in other planetary atmospheres.
Nitrogen is present in all living organisms in proteins, nucleic acids and other molecules. It typically makes up around 4% of the dry weight of plant matter, and around 3% of the weight of the human body. It is a large component of animal waste (for example, guano), usually in the form of urea, uric acid, ammonium compounds and derivatives of these nitrogenous products, which are essential nutrients for all plants that are unable to fix atmospheric nitrogen.
Nitrogen occurs naturally in a number of minerals, such as saltpetre (potassium nitrate), Chile saltpetre (sodium nitrate) and sal ammoniac (ammonium chloride). Most of these are relatively uncommon, partly because of the minerals' ready solubility in water. See also Nitrate minerals and Ammonium minerals.
Isotopesseealso Isotopes of nitrogen
There are two stable isotopes of nitrogen: 14N and 15N. By far the most common is 14N (99.634%), which is produced in the CNO cycle in stars. Of the ten isotopes produced synthetically, 13N has a half life of ten minutes and the remaining isotopes have half lives on the order of seconds or less. Biologically-mediated reactions (e.g., assimilation, nitrification, and denitrification) strongly control nitrogen dynamics in the soil. These reactions typically result in 15N enrichment of the substrate and depletion of the product.
0.73% of the molecular nitrogen in Earth's atmosphere is comprised of the isotopologue 14N15N and almost all the rest is 14N2.
Electromagnetic spectrumMolecular nitrogen (14N2) is largely transparent to infrared and visible radiation because it is a homonuclear molecule and thus has no dipole moment to couple to electromagnetic radiation at these wavelengths. Significant absorption occurs at extreme ultraviolet wavelengths, beginning around 100 nanometers. This is associated with electronic transitions in the molecule to states in which charge is not distributed evenly between nitrogen atoms. Nitrogen absorption leads to significant absorption of ultraviolet radiation in the Earth's upper atmosphere as well as in the atmospheres of other planetary bodies. For similar reasons, pure molecular nitrogen lasers typically emit light in the ultraviolet range.
Nitrogen also makes a contribution to visible air glow from the Earth's upper atmosphere, through electron impact excitation followed by emission. This visible blue air glow (seen in the polar aurora and in the re-entry glow of returning spacecraft) typically results not from molecular nitrogen, but rather from free nitrogen atoms combining with oxygen to form nitric oxide (NO).
HistoryNitrogen (Latin nitrogenium, where nitrum (from Greek nitron) means "saltpetre" (see niter), and genes means "forming") is formally considered to have been discovered by Daniel Rutherford in 1772, who called it noxious air or fixed air. That there was a fraction of air that did not support combustion was well known to the late 18th century chemist. Nitrogen was also studied at about the same time by Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley, who referred to it as burnt air or phlogisticated air. Nitrogen gas was inert enough that Antoine Lavoisier referred to it as azote, from the Greek word αζωτος meaning "lifeless". Animals died in it, and it was the principal component of air in which animals had suffocated and flames had burned to extinction. This term has become the French word for "nitrogen" and later spread out to many other languages.
Argon was discovered when it was noticed that nitrogen from air is not identical to nitrogen from chemical reactions.
Compounds of nitrogen were known in the Middle Ages. The alchemists knew nitric acid as aqua fortis (strong water). The mixture of nitric and hydrochloric acids was known as aqua regia (royal water), celebrated for its ability to dissolve gold (the king of metals). The earliest industrial and agricultural applications of nitrogen compounds involved uses in the form of saltpeter (sodium- or potassium nitrate), notably in gunpowder, and much later, as fertilizer.
Biological roleNitrogen is an essential part of amino acids and nucleic acids, both of which are essential to all life on Earth.
Molecular nitrogen in the atmosphere cannot be used directly by either plants or animals, and needs to be converted into nitrogen compounds, or "fixed," in order to be used by life. Precipitation often contains substantial quantities of ammonium and nitrate, both thought to be a result of nitrogen fixation by lightning and other atmospheric electric phenomena. However, because ammonium is preferentially retained by the forest canopy relative to atmospheric nitrate, most of the fixed nitrogen that reaches the soil surface under trees is in the form of nitrate. Soil nitrate is preferentially assimilated by tree roots relative to soil ammonium.
Specific bacteria (e.g. Rhizobium trifolium) possess nitrogenase enzymes which can fix atmospheric nitrogen (see nitrogen fixation) into a form (ammonium ion) which is chemically useful to higher organisms. This process requires a large amount of energy and anoxic conditions. Such bacteria may be free in the soil (e.g. Azotobacter) but normally exist in a symbiotic relationship in the root nodules of leguminous plants (e.g. clover, Trifolium species, or the soya bean plant, Glycine max). Nitrogen-fixing bacteria can be symbiotic with a number of unrelated plant species. Common examples are legumes, alders (Alnus) spp., lichens, Casuarina, Myrica, liverworts, and Gunnera.
As part of the symbiotic relationship, the plant subsequently converts the ammonium ion to nitrogen oxides and amino acids to form proteins and other biologically useful molecules, such as alkaloids. In return for the usable (fixed) nitrogen, the plant secretes sugars to the symbiotic bacteria.
Some plants are able to assimilate nitrogen directly in the form of nitrates which may be present in soil from natural mineral deposits, artificial fertilizers, animal waste, or organic decay (as the product of bacteria, but not bacteria specifically associated with the plant). Nitrates absorbed in this fashion are converted to nitrites by the enzyme nitrate reductase, and then converted to ammonia by another enzyme called nitrite reductase.
Nitrogen compounds are basic building blocks in animal biology. Animals use nitrogen-containing amino acids from plant sources, as starting materials for all nitrogen-compound animal biochemistry, including the manufacture of proteins and nucleic acids. Some plant-feeding insects are so dependent on nitrogen in their diet, that varying the amount of nitrogen fertilizer applied to a plant can affect the rate of reproduction of the insects feeding on it.
Soluble nitrate is an important limiting factor in the growth of certain bacteria in ocean waters. In many places in the world, artificial fertilizers applied to crop-lands to increase yields result in run-off delivery of soluble nitrogen to oceans at river mouths. This process can result in eutrophication of the water, as nitrogen-driven bacterial growth depletes water oxygen to the point that all higher organisms die. Well-known "dead zone" areas in the U.S. Gulf Coast and the Black Sea are due to this important polluting process.
Many saltwater fish manufacture large amounts of trimethylamine oxide to protect them from the high osmotic effects of their environment (conversion of this compound to dimethylamine is responsible for the early odor in unfresh saltwater fish: PMID 15186102). In animals, the free radical molecule nitric oxide (NO), which is derived from an amino acid, serves as an important regulatory molecule for circulation.
Animal metabolism of NO results in production of nitrite. Animal metabolism of nitrogen in proteins generally results in excretion of urea, while animal metabolism of nucleic acids results in excretion of urea and uric acid. The characteristic odor of animal flesh decay is caused by nitrogen-containing long-chain amines, such as putrescine and cadaverine.
Decay of organisms and their waste products may produce small amounts of nitrate, but most decay eventually returns nitrogen content to the atmosphere, as molecular nitrogen.
ReactionsNitrogen is generally unreactive at standard temperature and pressure. N2 reacts spontaneously with few reagents, being resilient to acids and bases as well as oxidants and most reductants. When nitrogen reacts spontaneously with a reagent, the net transformation is often called nitrogen fixation.
Nitrogen reacts with elemental lithium at STP. Lithium burns in an atmosphere of N2 to give lithium nitride:
- 6 Li + N2 → 2 Li3N
- 3 Mg + N2 → Mg3N2
When inhaled at high partial pressures (more than about 3 atmospheres, encountered at depths below about 30 m in scuba diving) nitrogen begins to act as an anesthetic agent. It can cause nitrogen narcosis, a temporary semi-anesthetized state of mental impairment similar to that caused by nitrous oxide.
Nitrogen also dissolves in the bloodstream and body fats. Rapid decompression (particularly in the case of divers ascending too quickly, or astronauts decompressing too quickly from cabin pressure to spacesuit pressure) can lead to a potentially fatal condition called decompression sickness (formerly known as caisson sickness or more commonly, the "bends"), when nitrogen bubbles form in the bloodstream, nerves, joints, and other sensitive or vital areas.
Direct skin contact with liquid nitrogen causes severe frostbite (cryogenic burns) within seconds, though not instantly on contact, depending on form of liquid nitrogen (liquid vs. mist) and surface area of the nitrogen-soaked material (soaked clothing or cotton causing more rapid damage than a spill of direct liquid to skin, which for a few seconds is protected by the Leidenfrost effect).
- Los Alamos National Laboratory – Nitrogen
- Chemistry of the Elements, N. N. Greenwood and A. Earnshaw. ISBN 0-08-022057-6
- Biochemistry, R.H. Garrett and C.M. Grisham. 2nd edition, 1999. ISBN 0-03-022318-0
dinitrogen in Afrikaans: Stikstof
dinitrogen in Arabic: نيتروجين
dinitrogen in Asturian: Nitróxenu
dinitrogen in Azerbaijani: Azot
dinitrogen in Bengali: নাইট্রোজেন
dinitrogen in Min Nan: N (goân-sò͘)
dinitrogen in Belarusian: Азот
dinitrogen in Bosnian: Dušik
dinitrogen in Bulgarian: Азот
dinitrogen in Catalan: Nitrogen
dinitrogen in Chuvash: Азот
dinitrogen in Czech: Dusík
dinitrogen in Corsican: Azotu
dinitrogen in Welsh: Nitrogen
dinitrogen in Danish: Kvælstof
dinitrogen in German: Stickstoff
dinitrogen in Estonian: Lämmastik
dinitrogen in Modern Greek (1453-): Άζωτο
dinitrogen in Spanish: Nitrógeno
dinitrogen in Esperanto: Azoto
dinitrogen in Basque: Nitrogeno
dinitrogen in Persian: نیتروژن
dinitrogen in French: Azote
dinitrogen in Friulian: Azôt
dinitrogen in Irish: Nítrigin
dinitrogen in Manx: Neetragien
dinitrogen in Galician: Nitróxeno
dinitrogen in Gujarati: નાઇટ્રોજન
dinitrogen in Korean: 질소
dinitrogen in Armenian: Ազոտ
dinitrogen in Hindi: नाइट्रोजन
dinitrogen in Upper Sorbian: Dusyk
dinitrogen in Croatian: Dušik
dinitrogen in Ido: Nitro
dinitrogen in Indonesian: Nitrogen
dinitrogen in Interlingua (International Auxiliary Language Association): Nitrogeno
dinitrogen in Icelandic: Nitur
dinitrogen in Italian: Azoto
dinitrogen in Hebrew: חנקן
dinitrogen in Pampanga: Nitrogen
dinitrogen in Georgian: აზოტი
dinitrogen in Kazakh: Азот
dinitrogen in Swahili (macrolanguage): Nitrojeni
dinitrogen in Haitian: Azòt
dinitrogen in Kurdish: Nîtrojen
dinitrogen in Latin: Nitrogenium
dinitrogen in Latvian: Slāpeklis
dinitrogen in Luxembourgish: Stéckstoff
dinitrogen in Lithuanian: Azotas
dinitrogen in Limburgan: Stikstof
dinitrogen in Lingala: Azoti
dinitrogen in Lojban: trano
dinitrogen in Hungarian: Nitrogén
dinitrogen in Macedonian: Азот
dinitrogen in Malayalam: നൈട്രജന്
dinitrogen in Maori: Hauota
dinitrogen in Marathi: नायट्रोजन
dinitrogen in Mongolian: Азотnah:Ehēcatehuiltic
dinitrogen in Dutch: Stikstof
dinitrogen in Japanese: 窒素
dinitrogen in Norwegian: Nitrogen
dinitrogen in Norwegian Nynorsk: Nitrogen
dinitrogen in Novial: Nitrogene
dinitrogen in Occitan (post 1500): Azòt
dinitrogen in Uzbek: Azot
dinitrogen in Low German: Stickstoff
dinitrogen in Polish: Azot
dinitrogen in Portuguese: Nitrogénio
dinitrogen in Kölsch: Stickstoff
dinitrogen in Romanian: Azot
dinitrogen in Quechua: Qullpachaq
dinitrogen in Russian: Азот
dinitrogen in Albanian: Azoti
dinitrogen in Sicilian: Azzotu
dinitrogen in Simple English: Nitrogen
dinitrogen in Slovak: Dusík
dinitrogen in Slovenian: Dušik
dinitrogen in Serbian: Азот
dinitrogen in Serbo-Croatian: Dušik
dinitrogen in Finnish: Typpi
dinitrogen in Swedish: Kväve
dinitrogen in Tamil: நைட்ரஜன்
dinitrogen in Telugu: నత్రజని
dinitrogen in Thai: ไนโตรเจน
dinitrogen in Vietnamese: Nitơ
dinitrogen in Tajik: Азот
dinitrogen in Turkish: Azot
dinitrogen in Ukrainian: Азот
dinitrogen in Contenese: 氮
dinitrogen in Samogitian: Azuots
dinitrogen in Chinese: 氮