Nitrogen

Nitrogen is the actinic aspect with the attribute N and diminutive cardinal 7. It was aboriginal apparent and abandoned by Scottish physician Daniel Rutherford in 1772. Although Carl Wilhelm Scheele and Henry Cavendish had apart done so at about the aforementioned time, Rutherford is about accorded the acclaim because his assignment was appear first. The name nitrogène was appropriate by French chemist Jean-Antoine-Claude Chaptal in 1790 aback it was begin that nitrogen was present in nitric acerbic and nitrates. Antoine Lavoisier appropriate instead the name azote, from the Greek ἀζωτικός "no life", as it is an asphyxiant gas; this name is instead acclimated in abounding languages, such as French, Italian, Russian, Romanian and Turkish, and appears in the English names of some nitrogen compounds such as hydrazine, azides and azo compounds.

Nitrogen is the lightest affiliate of accumulation 15 of the alternate table, generally alleged the pnictogens. It is a accepted aspect in the universe, estimated at about seventh in absolute affluence in the Milky Way and the Solar System. At accepted temperature and pressure, two atoms of the aspect bind to anatomy dinitrogen, a colourless and odorless diatomic gas with the blueprint N2. Dinitrogen forms about 78% of Earth's atmosphere, authoritative it the best abounding absolute element. Nitrogen occurs in all organisms, primarily in amino acids (and appropriately proteins), in the nucleic acids (DNA and RNA) and in the activity alteration atom adenosine triphosphate. The beastly anatomy contains about 3% nitrogen by mass, the fourth best abounding aspect in the anatomy afterwards oxygen, carbon, and hydrogen. The nitrogen aeon describes movement of the aspect from the air, into the abode and amoebic compounds, again aback into the atmosphere.

Many industrially important compounds, such as ammonia, nitric acid, amoebic nitrates (propellants and explosives), and cyanides, accommodate nitrogen. The acutely able amateur band in basal nitrogen (N≡N), the additional arch band in any diatomic atom afterwards carbon monoxide (CO),[2] dominates nitrogen chemistry. This causes adversity for both bacilli and industry in converting N2 into advantageous compounds, but at the aforementioned time agency that burning, exploding, or decomposing nitrogen compounds to anatomy nitrogen gas releases ample amounts of generally advantageous energy. Synthetically produced ammonia and nitrates are key automated fertilisers, and fertiliser nitrates are key pollutants in the eutrophication of baptize systems.

Apart from its use in fertilisers and energy-stores, nitrogen is a basic of amoebic compounds as assorted as Kevlar acclimated in high-strength bolt and cyanoacrylate acclimated in superglue. Nitrogen is a basic of every above pharmacological biologic class, including antibiotics. Abounding drugs are mimics or prodrugs of accustomed nitrogen-containing arresting molecules: for example, the amoebic nitrates nitroglycerin and nitroprusside ascendancy claret burden by metabolizing into nitric oxide. Abounding notable nitrogen-containing drugs, such as the accustomed caffeine and morphine or the constructed amphetamines, act on receptors of beastly neurotransmitters.Nitrogen compounds accept a actual continued history, ammonium chloride accepting been accustomed to Herodotus. They were able-bodied accustomed by the Middle Ages. Alchemists knew nitric acerbic as aqua fortis (strong water), as able-bodied as added nitrogen compounds such as ammonium salts and nitrate salts. The admixture of nitric and hydrochloric acids was accustomed as aqua regia (royal water), acclaimed for its adeptness to deliquesce gold, the baron of metals.[3]

The assay of nitrogen is attributed to the Scottish physician Daniel Rutherford in 1772, who alleged it baneful air.[4][5] Admitting he did not recognise it as an absolutely altered actinic substance, he acutely acclaimed it from Joseph Black's "fixed air", or carbon dioxide.[6] The actuality that there was a basic of air that does not abutment agitation was bright to Rutherford, although he was not acquainted that it was an element. Nitrogen was additionally advised at about the aforementioned time by Carl Wilhelm Scheele,[7] Henry Cavendish,[8] and Joseph Priestley,[9] who referred to it as burnt air or phlogisticated air. French chemist Antoine Lavoisier referred to nitrogen gas as "mephitic air" or azote, from the Greek chat άζωτικός (azotikos), "no life", due to it actuality mostly inert.[10][11] In an atmosphere of authentic nitrogen, animals died and bonfire were extinguished. Admitting Lavoisier's name was not accustomed in English, aback it was acicular out that about all gases (indeed, with the sole barring of oxygen) are mephitic, it is acclimated in abounding languages (French, Italian, Portuguese, Polish, Russian, Albanian, Turkish, etc.; the German Stickstoff analogously refers to the aforementioned characteristic, viz. ersticken "to asphyxiate or suffocate") and still charcoal in English in the accepted names of abounding nitrogen compounds, such as hydrazine and compounds of the azide ion. Finally, it led to the name "pnictogens" for the accumulation headed by nitrogen, from the Greek πνίγειν "to choke".[3]

The English chat nitrogen (1794) entered the accent from the French nitrogène, coined in 1790 by French chemist Jean-Antoine Chaptal (1756–1832),[12] from the French nitre (potassium nitrate, additionally alleged saltpeter) and the French suffix -gène, "producing", from the Greek -γενής (-genes, "begotten"). Chaptal's acceptation was that nitrogen is the capital allotment of nitric acid, which in about-face was produced from nitre. In beforehand times, niter had been abashed with Egyptian "natron" (sodium carbonate) – alleged νίτρον (nitron) in Greek – which, admitting the name, independent no nitrate.[13]

The ancient military, industrial, and agronomical applications of nitrogen compounds acclimated saltpeter (sodium nitrate or potassium nitrate), best conspicuously in gunpowder, and afterwards as fertiliser. In 1910, Lord Rayleigh apparent that an electrical acquittal in nitrogen gas produced "active nitrogen", a monatomic allotrope of nitrogen.[14] The "whirling billow of ablaze chicken light" produced by his accoutrement reacted with mercury to aftermath diminutive mercury nitride.[15]

For a continued time, sources of nitrogen compounds were limited. Accustomed sources originated either from assay or deposits of nitrates produced by atmospheric reactions. Nitrogen fixation by automated processes like the Frank–Caro action (1895–1899) and Haber–Bosch action (1908–1913) eased this curtailment of nitrogen compounds, to the admeasurement that bisected of all-around aliment assembly (see Applications) now relies on constructed nitrogen fertilisers.[16] At the aforementioned time, use of the Ostwald action (1902) to aftermath nitrates from automated nitrogen fixation accustomed the all-embracing automated assembly of nitrates as feedstock in the accomplish of explosives in the World Wars of the 20th century.[17][18]
Properties
Atomic
The shapes of the bristles orbitals active in nitrogen. The two colours appearance the appearance or assurance of the beachcomber action in anniversary region. From larboard to right: 1s, 2s (cutaway to appearance centralized structure), 2px, 2py, 2pz.

A nitrogen atom has seven electrons. In the arena state, they are abiding in the electron agreement 1s2
2s2
2p1
x2p1
y2p1
z. It accordingly has bristles valence electrons in the 2s and 2p orbitals, three of which (the p-electrons) are unpaired. It has one of the accomplished electronegativities amid the elements (3.04 on the Pauling scale), exceeded alone by chlorine (3.16), oxygen (3.44), and fluorine (3.98). (The ablaze blue-blooded gases, helium, neon, and argon, would apparently additionally be added electronegative, and in actuality are on the Allen scale.)[19] Following alternate trends, its single-bond covalent ambit of 71 pm is abate than those of boron (84 pm) and carbon (76 pm), while it is beyond than those of oxygen (66 pm) and fluorine (57 pm). The nitride anion, N3−, is abundant beyond at 146 pm, agnate to that of the oxide (O2−: 140 pm) and fluoride (F−: 133 pm) anions.[19] The aboriginal three ionisation energies of nitrogen are 1.402, 2.856, and 4.577 MJ·mol−1, and the sum of the fourth and fifth is 16.920 MJ·mol−1. Due to these actual aerial figures, nitrogen has no simple cationic chemistry.[20]

The abridgement of adorable nodes in the 2p subshell is anon amenable for abounding of the aberrant backdrop of the aboriginal row of the p-block, abnormally in nitrogen, oxygen, and fluorine. The 2p subshell is actual baby and has a actual agnate ambit to the 2s shell, facilitating alternate hybridisation. It additionally after-effects in actual ample electrostatic armament of allure amid the basis and the valence electrons in the 2s and 2p shells, consistent in actual aerial electronegativities. Hypervalency is about alien in the 2p elements for the aforementioned reason, because the aerial electronegativity makes it difficult for a baby nitrogen atom to be a axial atom in an electron-rich three-center four-electron band aback it would tend to allure the electrons acerb to itself. Thus, admitting nitrogen's position at the arch of accumulation 15 in the alternate table, its allure shows huge differences from that of its added congeners phosphorus, arsenic, antimony, and bismuth.[21]

Nitrogen may be agreeably compared to its accumbent neighbours carbon and oxygen as able-bodied as its vertical neighbours in the pnictogen column, phosphorus, arsenic, antimony, and bismuth. Although anniversary aeon 2 aspect from lithium to oxygen shows some similarities to the aeon 3 aspect in the abutting accumulation (from magnesium to chlorine; these are accustomed as askew relationships), their amount drops off abruptly accomplished the boron–silicon pair. The similarities of nitrogen to sulfur are mostly bound to sulfur nitride arena compounds aback both elements are the alone ones present.[22]

Nitrogen does not allotment the proclivity of carbon for catenation. Like carbon, nitrogen tends to anatomy ionic or brownish compounds with metals. Nitrogen forms an all-encompassing alternation of nitrides with carbon, including those with chain-, graphitic-, and fullerenic-like structures.[23]

It resembles oxygen with its aerial electronegativity and accessory adequacy for hydrogen bonding and the adeptness to anatomy allocation complexes by altruistic its abandoned pairs of electrons. There are some parallels amid the allure of ammonia NH3 and baptize H2O. For example, the accommodation of both compounds to be protonated to accord NH4+ and H3O+ or deprotonated to accord NH2− and OH−, with all of these able to be abandoned in solid compounds.[24]

Nitrogen shares with both its accumbent neighbours a alternative for basic assorted bonds, about with carbon, oxygen, or added nitrogen atoms, through pπ–pπ interactions.[22] Thus, for example, nitrogen occurs as diatomic molecules and accordingly has actual abundant lower melting (−210 °C) and baking credibility (−196 °C) than the blow of its group, as the N2 molecules are alone captivated calm by anemic van der Waals interactions and there are actual few electrons accessible to actualize cogent direct dipoles. This is not accessible for its vertical neighbours; thus, the nitrogen oxides, nitrites, nitrates, nitro-, nitroso-, azo-, and diazo-compounds, azides, cyanates, thiocyanates, and imino-derivatives acquisition no answer with phosphorus, arsenic, antimony, or bismuth. By the aforementioned token, however, the complication of the phosphorus oxoacids finds no answer with nitrogen.[22] Setting abreast their differences, nitrogen and phosphorus anatomy an all-encompassing alternation of compounds with one another; these accept chain, ring, and cage structures.[25]
Isotopes
Main article: Isotopes of nitrogen
Table of nuclides (Segrè chart) from carbon to fluorine (including nitrogen). Orange indicates proton discharge (nuclides alfresco the proton dribble line); blush for positron discharge (inverse beta decay); atramentous for abiding nuclides; dejected for electron discharge (beta decay); and violet for neutron discharge (nuclides alfresco the neutron dribble line). Proton cardinal increases activity up the vertical arbor and neutron cardinal activity to the appropriate on the accumbent axis.

Nitrogen has two abiding isotopes: 14N and 15N. The aboriginal is abundant added common, authoritative up 99.634% of accustomed nitrogen, and the additional (which is hardly heavier) makes up the actual 0.366%. This leads to an diminutive weight of about 14.007 u.[19] Both of these abiding isotopes are produced in the CNO aeon in stars, but 14N is added accepted as its neutron abduction is the rate-limiting step. 14N is one of the bristles abiding odd–odd nuclides (a nuclide accepting an odd cardinal of protons and neutrons); the added four are 2H, 6Li, 10B, and 180mTa.[26]

The about affluence of 14N and 15N is about connected in the atmosphere but can alter elsewhere, due to accustomed isotopic fractionation from biological redox reactions and the dehydration of accustomed ammonia or nitric acid.[27] Biologically advised reactions (e.g., assimilation, nitrification, and denitrification) acerb ascendancy nitrogen dynamics in the soil. These reactions about aftereffect in 15N accessory of the substrate and burning of the product.[28]

The abundant isotope 15N was aboriginal apparent by S. M. Naudé in 1929, anon afterwards abundant isotopes of the neighbouring elements oxygen and carbon were discovered.[29] It presents one of the everyman thermal neutron abduction cross-sections of all isotopes.[30] It is frequently acclimated in nuclear alluring resonance (NMR) spectroscopy to actuate the structures of nitrogen-containing molecules, due to its apportioned nuclear circuit of one-half, which offers advantages for NMR such as narrower band width. 14N, admitting additionally apparently usable, has an accumulation nuclear circuit of one and appropriately has a quadrupole moment that leads to added and beneath advantageous spectra.[19] 15N NMR about has complications not encountered in the added accepted 1H and 13C NMR spectroscopy. The low accustomed affluence of 15N (0.36%) decidedly reduces sensitivity, a botheration which is alone affronted by its low gyromagnetic ratio, (only 10.14% that of 1H). As a result, the signal-to-noise arrangement for 1H is about 300 times as abundant as that for 15N at the aforementioned alluring acreage strength.[31] This may be somewhat alleviated by isotopic accessory of 15N by actinic barter or apportioned distillation. 15N-enriched compounds accept the advantage that beneath accepted conditions, they do not abide actinic barter of their nitrogen atoms with atmospheric nitrogen, clashing compounds with labelled hydrogen, carbon, and oxygen isotopes that charge be kept abroad from the atmosphere.[19] The 15N:14N arrangement is frequently acclimated in abiding isotope assay in the fields of geochemistry, hydrology, paleoclimatology and paleoceanography, area it is alleged δ15N.[32]

Of the ten added isotopes produced synthetically, alignment from 12N to 23N, 13N has a half-life of ten account and the actual isotopes accept half-lives on the adjustment of abnormal (16N and 17N) or milliseconds. No added nitrogen isotopes are accessible as they would abatement alfresco the nuclear dribble lines, aperture out a proton or neutron.[33] Given the half-life difference, 13N is the best important nitrogen radioisotope, actuality almost abiding abundant to use in positron discharge tomography (PET), although its half-life is still abbreviate and appropriately it charge be produced at the area of the PET, for archetype in a cyclotron via proton battery of 16O bearing 13N and an alpha particle.[34]

The radioisotope 16N is the ascendant radionuclide in the coolant of pressurised baptize reactors or baking baptize reactors during accustomed operation, and appropriately it is a acute and actual indicator of leaks from the primary coolant arrangement to the accessory beef cycle, and is the primary agency of apprehension for such leaks. It is produced from 16O (in water) via an (n,p) acknowledgment in which the 16O atom captures a neutron and expels a proton. It has a abbreviate half-life of about 7.1 s,[33] but during its adulteration aback to 16O produces high-energy gamma radiation (5 to 7 MeV).[33][35] Because of this, admission to the primary coolant brim in a pressurised baptize reactor charge be belted during reactor ability operation.