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127-473: NO x gases are usually produced from the reaction between nitrogen and oxygen during combustion of fuels, such as hydrocarbons , in air; especially at high temperatures, such as in car engines. In areas of high motor vehicle traffic, such as in large cities, the nitrogen oxides emitted can be a significant source of air pollution. NO x gases are also produced naturally by lightning . NO x does not include nitrous oxide ( N 2 O ),

254-514: A dinitrogen complex to be discovered was [Ru(NH 3 ) 5 (N 2 )] (see figure at right), and soon many other such complexes were discovered. These complexes , in which a nitrogen molecule donates at least one lone pair of electrons to a central metal cation, illustrate how N 2 might bind to the metal(s) in nitrogenase and the catalyst for the Haber process : these processes involving dinitrogen activation are vitally important in biology and in

381-412: A lightning flash. In atmospheric chemistry , the term NO x refers to the total concentration of NO and NO 2 since the conversion between these two species is rapid in the stratosphere and troposphere. During daylight hours, these concentrations together with that of ozone are in steady state , also known as photostationary state (PSS); the ratio of NO to NO 2 is determined by

508-473: A bridging ligand, donating all three electron pairs from the triple bond ( μ 3 -N 2 ). A few complexes feature multiple N 2 ligands and some feature N 2 bonded in multiple ways. Since N 2 is isoelectronic with carbon monoxide (CO) and acetylene (C 2 H 2 ), the bonding in dinitrogen complexes is closely allied to that in carbonyl compounds, although N 2 is a weaker σ -donor and π -acceptor than CO. Theoretical studies show that σ donation

635-426: A dilute gas it is less dangerous and is thus used industrially to bleach and sterilise flour. Nitrogen tribromide (NBr 3 ), first prepared in 1975, is a deep red, temperature-sensitive, volatile solid that is explosive even at −100 °C. Nitrogen triiodide (NI 3 ) is still more unstable and was only prepared in 1990. Its adduct with ammonia, which was known earlier, is very shock-sensitive: it can be set off by

762-559: A fairly inert oxide of nitrogen that contributes less severely to air pollution, notwithstanding its involvement in ozone depletion and high global warming potential . NO y is the class of compounds comprising NO x and the NO z compounds produced from the oxidation of NO x which include nitric acid , nitrous acid (HONO), dinitrogen pentoxide ( N 2 O 5 ), peroxyacetyl nitrate (PAN), alkyl nitrates ( RONO 2 ), peroxyalkyl nitrates ( ROONO 2 ),

889-498: A liquid, it is a very good solvent with a high heat of vaporisation (enabling it to be used in vacuum flasks), that also has a low viscosity and electrical conductivity and high dielectric constant , and is less dense than water. However, the hydrogen bonding in NH 3 is weaker than that in H 2 O due to the lower electronegativity of nitrogen compared to oxygen and the presence of only one lone pair in NH 3 rather than two in H 2 O. It

1016-483: A long time, sources of nitrogen compounds were limited. Natural sources originated either from biology or deposits of nitrates produced by atmospheric reactions. Nitrogen fixation by industrial processes like the Frank–Caro process (1895–1899) and Haber–Bosch process (1908–1913) eased this shortage of nitrogen compounds, to the extent that half of global food production now relies on synthetic nitrogen fertilisers. At

1143-494: A preference for forming multiple bonds, typically with carbon, oxygen, or other nitrogen atoms, through p π –p π interactions. Thus, for example, nitrogen occurs as diatomic molecules and therefore has very much lower melting (−210 °C) and boiling points (−196 °C) than the rest of its group, as the N 2 molecules are only held together by weak van der Waals interactions and there are very few electrons available to create significant instantaneous dipoles. This

1270-591: A problem which is only exacerbated by its low gyromagnetic ratio , (only 10.14% that of H). As a result, the signal-to-noise ratio for H is about 300 times as much as that for N at the same magnetic field strength. This may be somewhat alleviated by isotopic enrichment of N by chemical exchange or fractional distillation. N-enriched compounds have the advantage that under standard conditions, they do not undergo chemical exchange of their nitrogen atoms with atmospheric nitrogen, unlike compounds with labelled hydrogen , carbon, and oxygen isotopes that must be kept away from

1397-470: A promising ceramic if not for the difficulty of working with and sintering it. In particular, the group 13 nitrides, most of which are promising semiconductors , are isoelectronic with graphite, diamond, and silicon carbide and have similar structures: their bonding changes from covalent to partially ionic to metallic as the group is descended. In particular, since the B–N unit is isoelectronic to C–C, and carbon

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1524-474: A ratio greater than or equal to the stoichiometric combustion requirement. Water Injection technology, whereby water is introduced into the combustion chamber, is also becoming an important means of NO x reduction through increased efficiency in the overall combustion process. Alternatively, the water (e.g. 10 to 50%) is emulsified into the fuel oil before the injection and combustion. This emulsification can either be made in-line (unstabilized) just before

1651-463: A significant dynamic surface coverage on Pluto and outer moons of the Solar System such as Triton . Even at the low temperatures of solid nitrogen it is fairly volatile and can sublime to form an atmosphere, or condense back into nitrogen frost. It is very weak and flows in the form of glaciers, and on Triton geysers of nitrogen gas come from the polar ice cap region. The first example of

1778-490: A source of NO x over the ocean. Then, photolysis of NO 2 leads to the formation of ozone and the further formation of hydroxyl radicals (·OH) through ozone photolysis. Since the major sink of methane in the atmosphere is by reaction with OH radicals, the NO x emissions from ship travel may lead to a net global cooling. However, NO x in the atmosphere may undergo dry or wet deposition and return to land in

1905-580: A special formulation of diesel fuel to produce less NO x relative to diesel fuel used in the other 49 states. This has been deemed necessary by the California Air Resources Board (CARB) to offset the combination of vehicle congestion, warm temperatures, extensive sunlight, PM, and topography that all contribute to the formation of ozone and smog. CARB has established a special regulation for Alternative Diesel Fuels to ensure that any new fuels, including biodiesel, coming into

2032-485: A third molecule required to stabilize the addition product. Nitric acid ( HNO 3 ) is highly soluble in liquid water in aerosol particles or cloud drops. NO 2 also reacts with ozone to form nitrate radical During the daytime, NO 3 is quickly photolyzed back to NO 2 , but at night it can react with a second NO 2 to form dinitrogen pentoxide . N 2 O 5 reacts rapidly with liquid water (in aerosol particles or cloud drops, but not in

2159-550: A tradeoff exists as high temperature combustion produces less PM or soot and results in greater power and fuel efficiency . Selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) reduce post combustion NO x by reacting the exhaust with urea or ammonia to produce nitrogen and water. SCR is now being used in ships, diesel trucks and in some diesel cars. The use of exhaust gas recirculation and catalytic converters in motor vehicle engines have significantly reduced vehicular emissions . NO x

2286-606: A very high energy density, that could be used as powerful propellants or explosives. Under extremely high pressures (1.1 million  atm ) and high temperatures (2000 K), as produced in a diamond anvil cell , nitrogen polymerises into the single-bonded cubic gauche crystal structure. This structure is similar to that of diamond , and both have extremely strong covalent bonds , resulting in its nickname "nitrogen diamond". At atmospheric pressure , molecular nitrogen condenses ( liquefies ) at 77  K (−195.79 ° C ) and freezes at 63 K (−210.01 °C) into

2413-465: Is oxatetrazole (N 4 O), an aromatic ring. Nitrous oxide (N 2 O), better known as laughing gas, is made by thermal decomposition of molten ammonium nitrate at 250 °C. This is a redox reaction and thus nitric oxide and nitrogen are also produced as byproducts. It is mostly used as a propellant and aerating agent for sprayed canned whipped cream , and was formerly commonly used as an anaesthetic. Despite appearances, it cannot be considered to be

2540-439: Is ONF 3 , which has aroused interest due to the short N–O distance implying partial double bonding and the highly polar and long N–F bond. Tetrafluorohydrazine, unlike hydrazine itself, can dissociate at room temperature and above to give the radical NF 2 •. Fluorine azide (FN 3 ) is very explosive and thermally unstable. Dinitrogen difluoride (N 2 F 2 ) exists as thermally interconvertible cis and trans isomers, and

2667-543: Is a nonmetal and the lightest member of group 15 of the periodic table , often called the pnictogens . It is a common element in the universe , estimated at seventh in total abundance in the Milky Way and the Solar System . At standard temperature and pressure , two atoms of the element bond to form N 2 , a colourless and odourless diatomic gas . N 2 forms about 78% of Earth's atmosphere , making it

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2794-419: Is a fuming, colourless liquid that smells similar to ammonia. Its physical properties are very similar to those of water (melting point 2.0 °C, boiling point 113.5 °C, density 1.00 g/cm ). Despite it being an endothermic compound, it is kinetically stable. It burns quickly and completely in air very exothermically to give nitrogen and water vapour. It is a very useful and versatile reducing agent and

2921-491: Is a more important factor allowing the formation of the M–N bond than π back-donation, which mostly only weakens the N–N bond, and end-on ( η ) donation is more readily accomplished than side-on ( η ) donation. Today, dinitrogen complexes are known for almost all the transition metals , accounting for several hundred compounds. They are normally prepared by three methods: Occasionally

3048-426: Is a secondary pollutant. Next to ozone and hydrogen peroxide (H 2 O 2 ), it is an important component of photochemical smog . Further peroxyacyl nitrates in the atmosphere are peroxypropionyl nitrate (PPN), peroxybutyryl nitrate (PBN), and peroxybenzoyl nitrate (PBzN). Chlorinated forms have also been observed. PAN is the most important peroxyacyl nitrate. PAN and its homologues reach about 5 to 20 percent of

3175-467: Is a weak base in aqueous solution ( p K b 4.74); its conjugate acid is ammonium , NH 4 . It can also act as an extremely weak acid, losing a proton to produce the amide anion, NH 2 . It thus undergoes self-dissociation, similar to water, to produce ammonium and amide. Ammonia burns in air or oxygen, though not readily, to produce nitrogen gas; it burns in fluorine with a greenish-yellow flame to give nitrogen trifluoride . Reactions with

3302-401: Is a weak diprotic acid with the structure HON=NOH (p K a1 6.9, p K a2 11.6). Acidic solutions are quite stable but above pH 4 base-catalysed decomposition occurs via [HONNO] to nitrous oxide and the hydroxide anion. Hyponitrites (involving the N 2 O 2 anion) are stable to reducing agents and more commonly act as reducing agents themselves. They are an intermediate step in

3429-399: Is a weaker base than ammonia. It is also commonly used as a rocket fuel. Hydrazine is generally made by reaction of ammonia with alkaline sodium hypochlorite in the presence of gelatin or glue: (The attacks by hydroxide and ammonia may be reversed, thus passing through the intermediate NHCl instead.) The reason for adding gelatin is that it removes metal ions such as Cu that catalyses

3556-418: Is added. As an alternative, PAN can also be synthesized in the gas phase via photolysis of acetone and NO 2 with a mercury lamp . Methyl nitrate (CH 3 ONO 2 ) is created as a by-product. The toxicity of PAN is higher than that of ozone. Eye irritations from photochemical smog are caused more by PAN and other trace gases than by ozone, which is only sparingly soluble. PAN is potentially involved in

3683-612: Is also evidence for the asymmetric red dimer O=N–O=N when nitric oxide is condensed with polar molecules. It reacts with oxygen to give brown nitrogen dioxide and with halogens to give nitrosyl halides. It also reacts with transition metal compounds to give nitrosyl complexes, most of which are deeply coloured. Blue dinitrogen trioxide (N 2 O 3 ) is only available as a solid because it rapidly dissociates above its melting point to give nitric oxide, nitrogen dioxide (NO 2 ), and dinitrogen tetroxide (N 2 O 4 ). The latter two compounds are somewhat difficult to study individually because of

3810-442: Is an oxidant that is more stable than ozone . Hence, it is more capable of long-range transport than ozone. It serves as a carrier for oxides of nitrogen (NOx) into rural regions and causes ozone formation in the global troposphere . PAN is produced in the atmosphere via photochemical oxidation of hydrocarbons to peroxyacetic acid radicals in the presence of nitrogen dioxide (NO 2 ). Since there are no direct emissions, it

3937-608: Is associated with a number of factors such as combustion temperature. As such, it can be observed that the vehicle drive cycle, or the load on the engine have more significant impact on NO x emissions than the type of fuel used. This may be especially true for modern, clean diesel vehicles that continuously monitor engine operation electronically and actively control engine parameters and exhaust system operations to limit NO x emission to less than 0.2 g/km. Low-temperature combustion or LTC technology may help reduce thermal formation of NO x during combustion, however

NOx - Misplaced Pages Continue

4064-562: Is associated with the combustion of nitrogen present in the feed material of cement rotary kilns, at between 300 °C and 800 °C, where it is considered a minor contributor. Thermal NO x refers to NO x formed through high temperature oxidation of the diatomic nitrogen found in combustion air. The formation rate is primarily a function of temperature and the residence time of nitrogen at that temperature. At high temperatures, usually above 1300 °C (2600 °F), molecular nitrogen ( N 2 ) and oxygen ( O 2 ) in

4191-416: Is common, where the nitrito form is usually less stable. Peroxyacetyl nitrate Peroxyacetyl nitrate is a peroxyacyl nitrate . It is a secondary pollutant present in photochemical smog . It is thermally unstable and decomposes into peroxyethanoyl radicals and nitrogen dioxide gas. It is a lachrymatory substance, meaning that it irritates the lungs and eyes. Peroxyacetyl nitrate, or PAN,

4318-611: Is emitted during its application, it is then reacted in atmosphere to form nitrogen oxides. This third source is attributed to the reaction of atmospheric nitrogen, N 2 , with radicals such as C, CH, and CH 2 fragments derived from fuel, rather than thermal or fuel processes. Occurring in the earliest stage of combustion, this results in the formation of fixed species of nitrogen such as NH ( nitrogen monohydride ), NCN ( diradical cyano nitrene ), HCN ( hydrogen cyanide ), H 2 CN ( dihydrogen cyanide ) and CN ( cyano radical) which can oxidize to NO. In fuels that contain nitrogen,

4445-404: Is essentially intermediate in size between boron and nitrogen, much of organic chemistry finds an echo in boron–nitrogen chemistry, such as in borazine ("inorganic benzene "). Nevertheless, the analogy is not exact due to the ease of nucleophilic attack at boron due to its deficiency in electrons, which is not possible in a wholly carbon-containing ring. The largest category of nitrides are

4572-430: Is highly temperature dependent, is recognized as the most relevant source when combusting natural gas. Fuel NO x tends to dominate during the combustion of fuels, such as coal, which have a significant nitrogen content, particularly when burned in combustors designed to minimise thermal NO x . The contribution of prompt NO x is normally considered negligible. A fourth source, called feed NO x

4699-437: Is intensifying global warming. There are also other indirect effects of NO x that can either increase or decrease the greenhouse effect. First of all, through the reaction of NO with HO 2 · radicals, OH radicals are recycled, which oxidize methane molecules, meaning NO x emissions can counter the effect of greenhouse gases. For instance, ship traffic emits a great amount of NO x which provides

4826-515: Is known. Industrially, ammonia (NH 3 ) is the most important compound of nitrogen and is prepared in larger amounts than any other compound because it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilisers. It is a colourless alkaline gas with a characteristic pungent smell. The presence of hydrogen bonding has very significant effects on ammonia, conferring on it its high melting (−78 °C) and boiling (−33 °C) points. As

4953-434: Is mildly toxic in concentrations above 100 mg/kg, but small amounts are often used to cure meat and as a preservative to avoid bacterial spoilage. It is also used to synthesise hydroxylamine and to diazotise primary aromatic amines as follows: Nitrite is also a common ligand that can coordinate in five ways. The most common are nitro (bonded from the nitrogen) and nitrito (bonded from an oxygen). Nitro-nitrito isomerism

5080-629: Is mostly unreactive at room temperature, but it will nevertheless react with lithium metal and some transition metal complexes. This is due to its bonding, which is unique among the diatomic elements at standard conditions in that it has an N≡N triple bond . Triple bonds have short bond lengths (in this case, 109.76 pm) and high dissociation energies (in this case, 945.41 kJ/mol), and are thus very strong, explaining dinitrogen's low level of chemical reactivity. Other nitrogen oligomers and polymers may be possible. If they could be synthesised, they may have potential applications as materials with

5207-489: Is much more common, making up 99.634% of natural nitrogen, and the second (which is slightly heavier) makes up the remaining 0.366%. This leads to an atomic weight of around 14.007 u. Both of these stable isotopes are produced in the CNO cycle in stars , but N is more common as its proton capture is the rate-limiting step. N is one of the five stable odd–odd nuclides (a nuclide having an odd number of protons and neutrons);

NOx - Misplaced Pages Continue

5334-682: Is not possible for its vertical neighbours; thus, the nitrogen oxides , nitrites , nitrates , nitro- , nitroso -, azo -, and diazo -compounds, azides , cyanates , thiocyanates , and imino -derivatives find no echo with phosphorus, arsenic, antimony, or bismuth. By the same token, however, the complexity of the phosphorus oxoacids finds no echo with nitrogen. Setting aside their differences, nitrogen and phosphorus form an extensive series of compounds with one another; these have chain, ring, and cage structures. Table of thermal and physical properties of nitrogen (N 2 ) at atmospheric pressure: Nitrogen has two stable isotopes : N and N. The first

5461-660: Is of interest for the preparation of explosives. It is a deliquescent , colourless crystalline solid that is sensitive to light. In the solid state it is ionic with structure [NO 2 ] [NO 3 ] ; as a gas and in solution it is molecular O 2 N–O–NO 2 . Hydration to nitric acid comes readily, as does analogous reaction with hydrogen peroxide giving peroxonitric acid (HOONO 2 ). It is a violent oxidising agent. Gaseous dinitrogen pentoxide decomposes as follows: Many nitrogen oxoacids are known, though most of them are unstable as pure compounds and are known only as aqueous solutions or as salts. Hyponitrous acid (H 2 N 2 O 2 )

5588-521: Is prepared by passing an electric discharge through nitrogen gas at 0.1–2 mmHg, which produces atomic nitrogen along with a peach-yellow emission that fades slowly as an afterglow for several minutes even after the discharge terminates. Given the great reactivity of atomic nitrogen, elemental nitrogen usually occurs as molecular N 2 , dinitrogen. This molecule is a colourless, odourless, and tasteless diamagnetic gas at standard conditions: it melts at −210 °C and boils at −196 °C. Dinitrogen

5715-443: Is produced from O (in water) via an (n,p) reaction , in which the O atom captures a neutron and expels a proton. It has a short half-life of about 7.1 s, but its decay back to O produces high-energy gamma radiation (5 to 7 MeV). Because of this, access to the primary coolant piping in a pressurised water reactor must be restricted during reactor power operation. It is a sensitive and immediate indicator of leaks from

5842-601: Is reduced to nitrite, then NO, then N 2 O and finally nitrogen. Through these processes, NO x is emitted to the atmosphere. A recent study conducted by the University of California Davis found that adding nitrogen fertilizer to soil in California is contributing 25 percent or more to state-wide NO x pollution levels. When nitrogen fertilizer is added to the soil, excess ammonium and nitrate not used by plants can be converted to NO by microorganisms in

5969-474: Is significant. It is a weak acid with p K a 3.35 at 18 °C. They may be titrimetrically analysed by their oxidation to nitrate by permanganate . They are readily reduced to nitrous oxide and nitric oxide by sulfur dioxide , to hyponitrous acid with tin (II), and to ammonia with hydrogen sulfide . Salts of hydrazinium N 2 H 5 react with nitrous acid to produce azides which further react to give nitrous oxide and nitrogen. Sodium nitrite

6096-482: Is similar to that in nitrogen, but one extra electron is added to a π * antibonding orbital and thus the bond order has been reduced to approximately 2.5; hence dimerisation to O=N–N=O is unfavourable except below the boiling point (where the cis isomer is more stable) because it does not actually increase the total bond order and because the unpaired electron is delocalised across the NO molecule, granting it stability. There

6223-404: Is smaller than those of boron (84 pm) and carbon (76 pm), while it is larger than those of oxygen (66 pm) and fluorine (57 pm). The nitride anion, N , is much larger at 146 pm, similar to that of the oxide (O : 140 pm) and fluoride (F : 133 pm) anions. The first three ionisation energies of nitrogen are 1.402, 2.856, and 4.577 MJ·mol , and the sum of

6350-523: Is the most important nitrogen radioisotope, being relatively long-lived enough to use in positron emission tomography (PET), although its half-life is still short and thus it must be produced at the venue of the PET, for example in a cyclotron via proton bombardment of O producing N and an alpha particle . The radioisotope N is the dominant radionuclide in the coolant of pressurised water reactors or boiling water reactors during normal operation. It

6477-400: Is the simplest stable molecule with an odd number of electrons. In mammals, including humans, it is an important cellular signalling molecule involved in many physiological and pathological processes. It is formed by catalytic oxidation of ammonia. It is a colourless paramagnetic gas that, being thermodynamically unstable, decomposes to nitrogen and oxygen gas at 1100–1200 °C. Its bonding

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6604-476: Is the strongest π donor known among ligands (the second-strongest is O ). Nitrido complexes are generally made by the thermal decomposition of azides or by deprotonating ammonia, and they usually involve a terminal {≡N} group. The linear azide anion ( N 3 ), being isoelectronic with nitrous oxide , carbon dioxide , and cyanate , forms many coordination complexes. Further catenation is rare, although N 4 (isoelectronic with carbonate and nitrate )

6731-640: Is thermodynamically stable, and most readily produced by the electrolysis of molten ammonium fluoride dissolved in anhydrous hydrogen fluoride . Like carbon tetrafluoride , it is not at all reactive and is stable in water or dilute aqueous acids or alkalis. Only when heated does it act as a fluorinating agent, and it reacts with copper , arsenic, antimony, and bismuth on contact at high temperatures to give tetrafluorohydrazine (N 2 F 4 ). The cations NF 4 and N 2 F 3 are also known (the latter from reacting tetrafluorohydrazine with strong fluoride-acceptors such as arsenic pentafluoride ), as

6858-602: Is used as an inert (oxygen-free) gas for commercial uses such as food packaging, and much of the rest is used as liquid nitrogen in cryogenic applications. Many industrially important compounds, such as ammonia , nitric acid, organic nitrates ( propellants and explosives ), and cyanides , contain nitrogen. The extremely strong triple bond in elemental nitrogen (N≡N), the second strongest bond in any diatomic molecule after carbon monoxide (CO), dominates nitrogen chemistry. This causes difficulty for both organisms and industry in converting N 2 into useful compounds , but at

6985-512: The Greek word άζωτικός (azotikos), "no life", due to it being asphyxiant . In an atmosphere of pure nitrogen, animals died and flames were extinguished. Though Lavoisier's name was not accepted in English since it was pointed out that all gases but oxygen are either asphyxiant or outright toxic, it is used in many languages (French, Italian, Portuguese, Polish, Russian, Albanian, Turkish, etc.;

7112-435: The anhydride of hyponitrous acid (H 2 N 2 O 2 ) because that acid is not produced by the dissolution of nitrous oxide in water. It is rather unreactive (not reacting with the halogens, the alkali metals, or ozone at room temperature, although reactivity increases upon heating) and has the unsymmetrical structure N–N–O (N≡N O ↔ N=N =O): above 600 °C it dissociates by breaking the weaker N–O bond. Nitric oxide (NO)

7239-575: The nucleic acids ( DNA and RNA ) and in the energy transfer molecule adenosine triphosphate . The human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes the movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere. Nitrogen is a constituent of every major pharmacological drug class, including antibiotics . Many drugs are mimics or prodrugs of natural nitrogen-containing signal molecules : for example,

7366-566: The 2s and 2p orbitals, three of which (the p-electrons) are unpaired. It has one of the highest electronegativities among the elements (3.04 on the Pauling scale), exceeded only by chlorine (3.16), oxygen (3.44), and fluorine (3.98). (The light noble gases , helium , neon , and argon , would presumably also be more electronegative, and in fact are on the Allen scale.) Following periodic trends, its single-bond covalent radius of 71 pm

7493-633: The French nitrogène , coined in 1790 by French chemist Jean-Antoine Chaptal (1756–1832), from the French nitre ( potassium nitrate , also called saltpetre ) and the French suffix -gène , "producing", from the Greek -γενής (-genes, "begotten"). Chaptal's meaning was that nitrogen is the essential part of nitric acid , which in turn was produced from nitre . In earlier times, nitre had been confused with Egyptian "natron" ( sodium carbonate ) – called νίτρον (nitron) in Greek ;– which, despite

7620-535: The German Stickstoff similarly refers to the same characteristic, viz. ersticken "to choke or suffocate") and still remains in English in the common names of many nitrogen compounds, such as hydrazine and compounds of the azide ion. Finally, it led to the name " pnictogens " for the group headed by nitrogen, from the Greek πνίγειν "to choke". The English word nitrogen (1794) entered the language from

7747-744: The Middle Ages. Alchemists knew nitric acid as aqua fortis (strong water), as well as other nitrogen compounds such as ammonium salts and nitrate salts. 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 discovery of nitrogen is attributed to the Scottish physician Daniel Rutherford in 1772, who called it noxious air . Though he did not recognise it as an entirely different chemical substance, he clearly distinguished it from Joseph Black's "fixed air" , or carbon dioxide. The fact that there

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7874-860: The N anion, although charge separation is not actually complete even for these highly electropositive elements. However, the alkali metal azides NaN 3 and KN 3 , featuring the linear N 3 anion, are well-known, as are Sr(N 3 ) 2 and Ba(N 3 ) 2 . Azides of the B-subgroup metals (those in groups 11 through 16 ) are much less ionic, have more complicated structures, and detonate readily when shocked. Many covalent binary nitrides are known. Examples include cyanogen ((CN) 2 ), triphosphorus pentanitride (P 3 N 5 ), disulfur dinitride (S 2 N 2 ), and tetrasulfur tetranitride (S 4 N 4 ). The essentially covalent silicon nitride (Si 3 N 4 ) and germanium nitride (Ge 3 N 4 ) are also known: silicon nitride, in particular, would make

8001-450: The N≡N bond may be formed directly within a metal complex, for example by directly reacting coordinated ammonia (NH 3 ) with nitrous acid (HNO 2 ), but this is not generally applicable. Most dinitrogen complexes have colours within the range white-yellow-orange-red-brown; a few exceptions are known, such as the blue [{Ti( η -C 5 H 5 ) 2 } 2 -(N 2 )]. Nitrogen bonds to almost all

8128-418: The ability to form coordination complexes by donating its lone pairs of electrons. There are some parallels between the chemistry of ammonia NH 3 and water H 2 O. For example, the capacity of both compounds to be protonated to give NH 4 and H 3 O or deprotonated to give NH 2 and OH , with all of these able to be isolated in solid compounds. Nitrogen shares with both its horizontal neighbours

8255-457: The air. Elevated production of NO x from lightning depends on the season and geographic location. The occurrence of lightning is more common over land near the equator in the inter-tropical convergence zone (ITCZ) during summer months. This area migrates slightly as seasons change. NO x production from lightning can be observed through satellite observations. Scientists Ott et al. estimated that each flash of lightning on average in

8382-417: The atmosphere. The N: N ratio is commonly used in stable isotope analysis in the fields of geochemistry , hydrology , paleoclimatology and paleoceanography , where it is called δ N . Of the thirteen other isotopes produced synthetically, ranging from N to N, N has a half-life of ten minutes and the remaining isotopes have half-lives less than eight seconds. Given the half-life difference, N

8509-435: The beta hexagonal close-packed crystal allotropic form. Below 35.4 K (−237.6 °C) nitrogen assumes the cubic crystal allotropic form (called the alpha phase). Liquid nitrogen , a colourless fluid resembling water in appearance, but with 80.8% of the density (the density of liquid nitrogen at its boiling point is 0.808 g/mL), is a common cryogen . Solid nitrogen has many crystalline modifications. It forms

8636-432: The combustion air dissociate into their atomic states and participate in a series of reactions. The three principal reactions (the extended Zel'dovich mechanism ) producing thermal NO x are: All three reactions are reversible. Zeldovich was the first to suggest the importance of the first two reactions. The last reaction of atomic nitrogen with the hydroxyl radical , HO, was added by Lavoie, Heywood and Keck to

8763-416: The combustion of the char portion of the fuels. This reaction occurs much more slowly than the volatile phase. Only around 20% of the char nitrogen is ultimately emitted as NO x , since much of the NO x that forms during this process is reduced to nitrogen by the char, which is nearly pure carbon. Nitrogen oxides are released during manufacturing of nitrogen fertilizers. Though nitrous oxide

8890-409: The concentration of ozone and peroxide compounds, especially peroxyacetyl nitrate (PAN). Children, people with lung diseases such as asthma , and people who work or exercise outside are particularly susceptible to adverse effects of smog such as damage to lung tissue and reduction in lung function. NO 2 is further oxidized in the gas phase during daytime by reaction with OH where M denotes

9017-402: The concentration of ozone in urban areas. At lower temperatures, it is stable and can be transported over long distances, providing nitrogen oxides to otherwise unpolluted areas. At higher temperatures, it decomposes into NO 2 and the peroxyacetyl radical. The decay of PAN in the atmosphere is mainly thermal. Thus, the long-range transport occurs through cold regions of the atmosphere, whereas

9144-416: The conjugate acid of the azide anion, and is similarly analogous to the hydrohalic acids . All four simple nitrogen trihalides are known. A few mixed halides and hydrohalides are known, but are mostly unstable; examples include NClF 2 , NCl 2 F, NBrF 2 , NF 2 H, NFH 2 , NCl 2 H , and NClH 2 . Nitrogen trifluoride (NF 3 , first prepared in 1928) is a colourless and odourless gas that

9271-555: The continuity of bonding types instead of the discrete and separate types that it implies. They are normally prepared by directly reacting a metal with nitrogen or ammonia (sometimes after heating), or by thermal decomposition of metal amides: Many variants on these processes are possible. The most ionic of these nitrides are those of the alkali metals and alkaline earth metals , Li 3 N (Na, K, Rb, and Cs do not form stable nitrides for steric reasons) and M 3 N 2 (M = Be, Mg, Ca, Sr, Ba). These can formally be thought of as salts of

9398-599: The countryside and in suburbs, while in central London and on major roads NO emissions are able to "mop up" ozone to form NO 2 and oxygen. NO x also readily reacts with common organic chemicals, and even ozone, to form a wide variety of toxic products: nitroarenes , nitrosamines and also the nitrate radical some of which may cause DNA mutations . Recently another pathway, via NO x , to ozone has been found that predominantly occurs in coastal areas via formation of nitryl chloride when NO x comes into contact with salt mist. The direct effect of

9525-607: The decomposition takes place at warmer levels. PAN can also be photolysed by UV radiation. It is a reservoir gas that serves both as a source and a sink of RO x - and NO x radicals. Nitrogen oxides from PAN decomposition enhance ozone production in the lower troposphere . The natural concentration of PAN in the atmosphere is below 0.1 μg/m . Measurements in German cities showed values up to 25 μg/m . Peak values above 200 μg/m have been measured in Los Angeles in

9652-417: The destruction of hydrazine by reaction with monochloramine (NH 2 Cl) to produce ammonium chloride and nitrogen. Hydrogen azide (HN 3 ) was first produced in 1890 by the oxidation of aqueous hydrazine by nitrous acid. It is very explosive and even dilute solutions can be dangerous. It has a disagreeable and irritating smell and is a potentially lethal (but not cumulative) poison. It may be considered

9779-487: The eastern United States can expect to see increases in NO x and in turn, changes in the types of trees which predominate. Due to human activity and climate change , the maples , sassafras , and tulip poplar have been pushing out the beneficial oak , beech , and hickory . The team determined that the first three tree species, maples, sassafras, and tulip poplar, are associated with ammonia-oxidizing bacteria known to "emit reactive nitrogen from soil." By contrast,

9906-734: The elements in the periodic table except the first two noble gases , helium and neon , and some of the very short-lived elements after bismuth , creating an immense variety of binary compounds with varying properties and applications. Many binary compounds are known: with the exception of the nitrogen hydrides, oxides, and fluorides, these are typically called nitrides . Many stoichiometric phases are usually present for most elements (e.g. MnN, Mn 6 N 5 , Mn 3 N 2 , Mn 2 N, Mn 4 N, and Mn x N for 9.2 < x < 25.3). They may be classified as "salt-like" (mostly ionic), covalent, "diamond-like", and metallic (or interstitial ), although this classification has limitations generally stemming from

10033-526: The emission of NO x has positive contribution to the greenhouse effect. Instead of reacting with ozone in Reaction 3, NO can also react with HO 2 · and organic peroxyradicals ( RO 2 · ) and thus increase the concentration of ozone. Once the concentration of NO x exceeds a certain level, atmospheric reactions result in net ozone formation. Since tropospheric ozone can absorb infrared radiation, this indirect effect of NO x

10160-467: The equilibrium between them, although sometimes dinitrogen tetroxide can react by heterolytic fission to nitrosonium and nitrate in a medium with high dielectric constant. Nitrogen dioxide is an acrid, corrosive brown gas. Both compounds may be easily prepared by decomposing a dry metal nitrate. Both react with water to form nitric acid . Dinitrogen tetroxide is very useful for the preparation of anhydrous metal nitrates and nitrato complexes, and it became

10287-475: The exothermic reaction 2 . Equation 4 relates the concentrations of NO x and ozone, and is known as the Leighton relationship . The time τ {\displaystyle \tau } that is needed to reach a steady state among NO x and ozone is dominated by reaction ( 3 ), which reverses reactions ( 1 )+( 2 ): for mixing ratio of NO, [NO] = 10 part per billion (ppb),

10414-404: The extreme heating and cooling within a lightning strike. This causes stable molecules such as N 2 and O 2 to convert into significant amounts of NO similar to the process that occurs during high temperature fuel combustion. NO x from lightning can become oxidized to produce nitric acid ( HNO 3 ), this can be precipitated out as acid rain or deposited onto particles in

10541-421: The first gases to be identified: N 2 O ( nitrous oxide ), NO ( nitric oxide ), N 2 O 3 ( dinitrogen trioxide ), NO 2 ( nitrogen dioxide ), N 2 O 4 ( dinitrogen tetroxide ), N 2 O 5 ( dinitrogen pentoxide ), N 4 O ( nitrosylazide ), and N(NO 2 ) 3 ( trinitramide ). All are thermally unstable towards decomposition to their elements. One other possible oxide that has not yet been synthesised

10668-669: The form of HNO 3 / NO − 3 . Through this way, the deposition leads to nitrogen fertilization and the subsequent formation of nitrous oxide ( N 2 O ) in soil, which is another greenhouse gas. In conclusion, considering several direct and indirect effects, NO x emissions have a negative contribution to global warming. NO x in the atmosphere is removed through several pathways. During daytime, NO 2 reacts with hydroxyl radicals (·OH) and forms nitric acid ( HNO 3 ), which can easily be removed by dry and wet deposition. Organic peroxyradicals ( RO 2 · ) can also react with NO and NO 2 and result in

10795-787: The formation of organic nitrates . These are ultimately broken down to inorganic nitrate, which is a useful nutrient for plants. During nighttime, NO 2 and NO can form nitrous acid (HONO) through surface-catalyzed reaction. Although the reaction is relatively slow, it is an important reaction in urban areas. In addition, the nitrate radical ( NO 3 ) is formed by the reaction between NO 2 and ozone. At night, NO 3 further reacts with NO 2 and establishes an equilibrium reaction with dinitrogen pentoxide ( N 2 O 5 ). Via heterogeneous reaction, N 2 O 5 reacts with water vapor or liquid water and forms nitric acid ( HNO 3 ). As mentioned above, nitric acid can be removed through wet and dry deposition and this results in

10922-496: The fourth and fifth is 16.920 MJ·mol . Due to these very high figures, nitrogen has no simple cationic chemistry. The lack of radial nodes in the 2p subshell is directly responsible for many of the anomalous properties of the first row of the p-block , especially in nitrogen, oxygen, and fluorine. The 2p subshell is very small and has a very similar radius to the 2s shell, facilitating orbital hybridisation . It also results in very large electrostatic forces of attraction between

11049-407: The gas phase) to form HNO 3 , These are thought to be the principal pathways for formation of nitric acid in the atmosphere. This nitric acid contributes to acid rain or may deposit to soil, where it makes nitrate , which is of use to growing plants. The aqueous phase reaction is too slow to be of any significance in the atmosphere. Nitric oxide is produced during thunderstorms due to

11176-437: The head of group 15 in the periodic table, its chemistry shows huge differences from that of its heavier congeners phosphorus , arsenic , antimony , and bismuth . Nitrogen may be usefully compared to its horizontal neighbours' carbon and oxygen as well as its vertical neighbours in the pnictogen column, phosphorus, arsenic, antimony, and bismuth. Although each period 2 element from lithium to oxygen shows some similarities to

11303-672: The incidence of prompt NO x is comparatively small and it is generally only of interest for the most exacting emission targets. There is strong evidence that NO x respiratory exposure can trigger and exacerbate existing asthma symptoms, and may even lead to the development of asthma over longer periods of time. It has also been associated with heart disease, diabetes, birth outcomes, and all-cause mortality, but these nonrespiratory effects are less well-established. NO x reacts with ammonia , moisture, and other compounds to form nitric acid vapor and related particles. NO x reacts with volatile organic compounds in

11430-408: The initial stages of combustion. During the release and before the oxidation of the volatiles, nitrogen reacts to form several intermediaries which are then oxidized into NO. If the volatiles evolve into a reducing atmosphere, the nitrogen evolved can readily be made to form nitrogen gas, rather than NO x . The second pathway involves the combustion of nitrogen contained in the char matrix during

11557-404: The injection or as a drop-in fuel with chemical additives for long-term emulsion stability (stabilized). Excessive water addition facilitates hot corrosion, which is the primary reason why dry low- NO x technologies are favored today besides the requirement of a more complex system. Nitrogen Nitrogen is a chemical element ; it has symbol N and atomic number 7. Nitrogen

11684-418: The intensity of sunshine (which converts NO 2 to NO) and the concentration of ozone (which reacts with NO to again form NO 2 ). In other words, the concentration of ozone in the atmosphere is determined by the ratio of these two species. The symbol M {\displaystyle {\ce {M}}} represents a "third body", a molecular species that is required to carry away energy from

11811-505: The interstitial nitrides of formulae MN, M 2 N, and M 4 N (although variable composition is perfectly possible), where the small nitrogen atoms are positioned in the gaps in a metallic cubic or hexagonal close-packed lattice. They are opaque, very hard, and chemically inert, melting only at very high temperatures (generally over 2500 °C). They have a metallic lustre and conduct electricity as do metals. They hydrolyse only very slowly to give ammonia or nitrogen. The nitride anion (N )

11938-458: The market do not substantially increase NO x emissions. The reduction of NO x emissions is one of the most important challenges for advances in vehicle technology. While diesel vehicles sold in the US since 2010 are dramatically cleaner than previous diesel vehicles, urban areas continue to seek more ways to reduce the formation of smog and ozone. NO x formation during combustion

12065-403: The mechanism and makes a significant contribution to the formation of thermal NO x . It is estimated that transportation fuels cause 54% of the anthropogenic (i.e. human-caused) NO x . The major source of NO x production from nitrogen-bearing fuels such as certain coals and oil, is the conversion of fuel bound nitrogen to NO x during combustion. During combustion,

12192-485: The most abundant chemical species in air. Because of the volatility of nitrogen compounds, nitrogen is relatively rare in the solid parts of the Earth. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772 and independently by Carl Wilhelm Scheele and Henry Cavendish at about the same time. The name nitrogène was suggested by French chemist Jean-Antoine-Claude Chaptal in 1790 when it

12319-525: The name, contained no nitrate. The earliest military, industrial, and agricultural applications of nitrogen compounds used saltpetre ( sodium nitrate or potassium nitrate), most notably in gunpowder , and later as fertiliser . In 1910, Lord Rayleigh discovered that an electrical discharge in nitrogen gas produced "active nitrogen", a monatomic allotrope of nitrogen. The "whirling cloud of brilliant yellow light" produced by his apparatus reacted with mercury to produce explosive mercury nitride . For

12446-431: The nitrate radical ( NO 3 ), and peroxynitric acid ( HNO 4 ). Because of energy limitations, oxygen and nitrogen do not react at ambient temperatures. But at high temperatures, they undergo an endothermic reaction producing various oxides of nitrogen. Such temperatures arise inside an internal combustion engine or a power station boiler , during the combustion of a mixture of air and fuel, and naturally in

12573-426: The nitrogen bound in the fuel is released as a free radical and ultimately forms free N 2 , or NO. Fuel can contribute as much as 50% of total NO x emissions through the combusting oil and as much as 80% through the combusting of coal Although the complete mechanism is not fully understood, there are two primary pathways of formation. The first involves the oxidation of volatile nitrogen species during

12700-574: The nitryl halides (XNO 2 ). The first is very reactive gases that can be made by directly halogenating nitrous oxide. Nitrosyl fluoride (NOF) is colourless and a vigorous fluorinating agent. Nitrosyl chloride (NOCl) behaves in much the same way and has often been used as an ionising solvent. Nitrosyl bromide (NOBr) is red. The reactions of the nitryl halides are mostly similar: nitryl fluoride (FNO 2 ) and nitryl chloride (ClNO 2 ) are likewise reactive gases and vigorous halogenating agents. Nitrogen forms nine molecular oxides, some of which were

12827-436: The nucleus and the valence electrons in the 2s and 2p shells, resulting in very high electronegativities. Hypervalency is almost unknown in the 2p elements for the same reason, because the high electronegativity makes it difficult for a small nitrogen atom to be a central atom in an electron-rich three-center four-electron bond since it would tend to attract the electrons strongly to itself. Thus, despite nitrogen's position at

12954-437: The number of lightning strikes occurring on Earth. Therefore, space weather can be a major driving force of lightning-produced atmospheric NO x . Atmospheric constituents such as nitrogen oxides can be stratified vertically in the atmosphere. Ott noted that the lightning-produced NO x is typically found at altitudes greater than 5 km, while combustion and biogenic (soil) NO x are typically found near

13081-410: The organic nitrates nitroglycerin and nitroprusside control blood pressure by metabolising into nitric oxide . Many notable nitrogen-containing drugs, such as the natural caffeine and morphine or the synthetic amphetamines , act on receptors of animal neurotransmitters . Nitrogen compounds have a very long history, ammonium chloride having been known to Herodotus . They were well-known by

13208-412: The other four are H , Li, B, and Ta. The relative abundance of N and N is practically constant in the atmosphere but can vary elsewhere, due to natural isotopic fractionation from biological redox reactions and the evaporation of natural ammonia or nitric acid . Biologically mediated reactions (e.g., assimilation , nitrification , and denitrification ) strongly control nitrogen dynamics in

13335-421: The other nonmetals are very complex and tend to lead to a mixture of products. Ammonia reacts on heating with metals to give nitrides. Many other binary nitrogen hydrides are known, but the most important are hydrazine (N 2 H 4 ) and hydrogen azide (HN 3 ). Although it is not a nitrogen hydride, hydroxylamine (NH 2 OH) is similar in properties and structure to ammonia and hydrazine as well. Hydrazine

13462-478: The oxidation of ammonia to nitrite, which occurs in the nitrogen cycle . Hyponitrite can act as a bridging or chelating bidentate ligand. Nitrous acid (HNO 2 ) is not known as a pure compound, but is a common component in gaseous equilibria and is an important aqueous reagent: its aqueous solutions may be made from acidifying cool aqueous nitrite ( NO 2 , bent) solutions, although already at room temperature disproportionation to nitrate and nitric oxide

13589-704: The period 3 element in the next group (from magnesium to chlorine; these are known as diagonal relationships ), their degree drops off abruptly past the boron–silicon pair. The similarities of nitrogen to sulfur are mostly limited to sulfur nitride ring compounds when both elements are the only ones present. Nitrogen does not share the proclivity of carbon for catenation . Like carbon, nitrogen tends to form ionic or metallic compounds with metals. Nitrogen forms an extensive series of nitrides with carbon, including those with chain-, graphitic- , and fullerenic -like structures. It resembles oxygen with its high electronegativity and concomitant capability for hydrogen bonding and

13716-517: The presence of sunlight to form ozone . Ozone can cause adverse effects such as damage to lung tissue and reduction in lung function mostly in susceptible populations (children, elderly, asthmatics). Ozone can be transported by wind currents and cause health impacts far from the original sources. The American Lung Association estimates that nearly 50 percent of United States inhabitants live in counties that are not in ozone compliance. In South East England, ground level ozone pollution tends to be highest in

13843-583: The primary coolant system to the secondary steam cycle and is the primary means of detection for such leaks. Atomic nitrogen, also known as active nitrogen, is highly reactive, being a triradical with three unpaired electrons. Free nitrogen atoms easily react with most elements to form nitrides, and even when two free nitrogen atoms collide to produce an excited N 2 molecule, they may release so much energy on collision with even such stable molecules as carbon dioxide and water to cause homolytic fission into radicals such as CO and O or OH and H. Atomic nitrogen

13970-522: The production of fertilisers. Dinitrogen is able to coordinate to metals in five different ways. The more well-characterised ways are the end-on M←N≡N ( η ) and M←N≡N→M ( μ , bis- η ), in which the lone pairs on the nitrogen atoms are donated to the metal cation. The less well-characterised ways involve dinitrogen donating electron pairs from the triple bond, either as a bridging ligand to two metal cations ( μ , bis- η ) or to just one ( η ). The fifth and unique method involves triple-coordination as

14097-663: The removal of NO x from the atmosphere. Biodiesel and its blends in general are known to reduce harmful tailpipe emissions such as: carbon monoxide ; particulate matter (PM), otherwise known as soot ; and unburned hydrocarbon emissions. While earlier studies suggested biodiesel could sometimes decrease NO x and sometimes increase NO x emissions, subsequent investigation has shown that blends of up to 20% biodiesel in USEPA-approved diesel fuel have no significant impact on NO x emissions compared with regular diesel . The state of California uses

14224-599: The same time it means that burning, exploding, or decomposing nitrogen compounds to form nitrogen gas releases large amounts of often useful energy. Synthetically produced ammonia and nitrates are key industrial fertilisers , and fertiliser nitrates are key pollutants in the eutrophication of water systems. Apart from its use in fertilisers and energy stores, nitrogen is a constituent of organic compounds as diverse as aramids used in high-strength fabric and cyanoacrylate used in superglue . Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins ), in

14351-583: The same time, use of the Ostwald process (1902) to produce nitrates from industrial nitrogen fixation allowed the large-scale industrial production of nitrates as feedstock in the manufacture of explosives in the World Wars of the 20th century. A nitrogen atom has seven electrons. In the ground state, they are arranged in the electron configuration 1s 2s 2p x 2p y 2p z . It, therefore, has five valence electrons in

14478-429: The second half of the 20th century (1 ppm of PAN corresponds to 4370 μg/m ). Due to the complexity of the measurement setup, only sporadic measurements are available. PAN is a greenhouse gas . PAN can be produced in a lipophilic solvent from peroxyacetic acid . For the synthesis, concentrated sulfuric acid is added to degassed n - tridecane and peroxyacetic acid in an ice bath. Next, concentrated nitric acid

14605-493: The second three tree species, oak, beech and hickory, are associated with microbes that "absorb reactive nitrogen oxides," and thus can have a positive impact on the nitrogen oxide component of air quality. Nitrogen oxide release from forest soils is expected to be highest in Indiana, Illinois, Michigan, Kentucky and Ohio. The three primary sources of NO x in combustion processes: Thermal NO x formation, which

14732-542: The several mid-latitude and subtropical thunderstorms studied turned 7 kg (15 lb) of nitrogen into chemically reactive NO x . With 1.4 billion lightning flashes per year, multiplied by 7 kilograms per lightning strike, they estimated the total amount of NO x produced by lightning per year is 8.6 million tonnes. However, NO x emissions resulting from fossil fuel combustion are estimated at 28.5 million tonnes. A recent discovery indicated that cosmic ray and solar flares can significantly influence

14859-490: The soil, which escapes into the air. NO x is a precursor for smog formation which is already a known issue for the state of California. In addition to contributing to smog, when nitrogen fertilizer is added to the soil and the excess is released in the form of NO, or leached as nitrate this can be a costly process for the farming industry. A 2018 study by the Indiana University determined that forests in

14986-451: The soil. These reactions typically result in N enrichment of the substrate and depletion of the product . The heavy isotope N was first discovered by S. M. Naudé in 1929, and soon after heavy isotopes of the neighbouring elements oxygen and carbon were discovered. It presents one of the lowest thermal neutron capture cross-sections of all isotopes. It is frequently used in nuclear magnetic resonance (NMR) spectroscopy to determine

15113-424: The sources at near surface elevation (where it can cause the most significant health effects). Agricultural fertilization and the use of nitrogen fixing plants also contribute to atmospheric NO x , by promoting nitrogen fixation by microorganisms. The nitrification process transforms ammonia into nitrate. Denitrification is basically the reverse process of nitrification. During denitrification, nitrate

15240-520: The storable oxidiser of choice for many rockets in both the United States and USSR by the late 1950s. This is because it is a hypergolic propellant in combination with a hydrazine -based rocket fuel and can be easily stored since it is liquid at room temperature. The thermally unstable and very reactive dinitrogen pentoxide (N 2 O 5 ) is the anhydride of nitric acid , and can be made from it by dehydration with phosphorus pentoxide . It

15367-489: The structures of nitrogen-containing molecules, due to its fractional nuclear spin of one-half, which offers advantages for NMR such as narrower line width. N, though also theoretically usable, has an integer nuclear spin of one and thus has a quadrupole moment that leads to wider and less useful spectra. N NMR nevertheless has complications not encountered in the more common H and C NMR spectroscopy. The low natural abundance of N (0.36%) significantly reduces sensitivity,

15494-451: The time constant is 40 minutes; for [NO] = 1 ppb, 4 minutes. When NO x and volatile organic compounds (VOCs) react in the presence of sunlight, they form photochemical smog , a significant form of air pollution. The presence of photochemical smog increases during the summer when the incident solar radiation is higher. The emitted hydrocarbons from industrial activities and transportation react with NO x quickly and increase

15621-420: The touch of a feather, shifting air currents, or even alpha particles . For this reason, small amounts of nitrogen triiodide are sometimes synthesised as a demonstration to high school chemistry students or as an act of "chemical magic". Chlorine azide (ClN 3 ) and bromine azide (BrN 3 ) are extremely sensitive and explosive. Two series of nitrogen oxohalides are known: the nitrosyl halides (XNO) and

15748-412: Was a component of air that does not support combustion was clear to Rutherford, although he was not aware that it was an element. 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 . French chemist Antoine Lavoisier referred to nitrogen gas as " mephitic air " or azote , from

15875-442: Was first found as a product of the thermal decomposition of FN 3 . Nitrogen trichloride (NCl 3 ) is a dense, volatile, and explosive liquid whose physical properties are similar to those of carbon tetrachloride , although one difference is that NCl 3 is easily hydrolysed by water while CCl 4 is not. It was first synthesised in 1811 by Pierre Louis Dulong , who lost three fingers and an eye to its explosive tendencies. As

16002-566: Was found that nitrogen was present in nitric acid and nitrates . Antoine Lavoisier suggested instead the name azote , from the Ancient Greek : ἀζωτικός "no life", as it is an asphyxiant gas ; this name is used in a number of languages, and appears in the English names of some nitrogen compounds such as hydrazine , azides and azo compounds . Elemental nitrogen is usually produced from air by pressure swing adsorption technology. About 2/3 of commercially produced elemental nitrogen

16129-542: Was the main focus of the Volkswagen emissions violations . Other technologies such as flameless oxidation ( FLOX ) and staged combustion significantly reduce thermal NO x in industrial processes. Bowin low NO x technology is a hybrid of staged-premixed-radiant combustion technology with major surface combustion preceded by minor radiant combustion. In the Bowin burner, air and fuel gas are premixed at

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