NITROGEN

[14.00643,14.00728]14.007±0.001(abridged) 1st: 1402.3 kJ/mol2nd: 2856 kJ/mol3rd: 4578.1 kJ/mol(more) ve viewtalkedit Nitrogenis achemical element; it hassymbolNandatomic number7.‍‍‍‍‍‍​​​‍​​​​​​ Nitrogen is anonmetaland the lightest member ofgroup 15of theperiodic table, often called thepnictogens. It is a common element in theuniverse, estimated atseventh in total abundancein theMilky Wayand theSolar System. Atstandard temperature and pressure, two atoms of the elementbondto form N2, a colourless and odourlessdiatomicgas. N2forms about 78% ofEarth's atmosphere, making it 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 physicianDaniel Rutherfordin 1772 and independently byCarl Wilhelm ScheeleandHenry Cavendishat about the same time. The namenitrogènewas suggested by French chemistJean-Antoine-Claude Chaptalin 1790 when it was found that nitrogen was present innitric acidandnitrates.Antoine Lavoisiersuggested instead the nameazote, from theAncient Greek:ἀζωτικός"no life", as it is anasphyxiant gas; this name is used in a number of languages, and appears in the English names of some nitrogen compounds such ashydrazine,azidesandazo compounds. Elemental nitrogen is usually produced from air bypressure swing adsorptiontechnology. About 2/3 of commercially produced elemental nitrogen is used as an inert (oxygen-free) gas for commercial uses such as food packaging, and much of the rest is used asliquid nitrogenincryogenicapplications. Many industrially important compounds, such asammonia, nitric acid, organic nitrates (propellantsandexplosives), andcyanides, contain nitrogen. The extremely strongtriple bondin elemental nitrogen (N≡N), the second strongest bond in anydiatomic moleculeaftercarbon monoxide(CO),dominates nitrogen chemistry. This causes difficulty for both organisms and industry in converting N2into usefulcompounds, but at 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 industrialfertilisers, and fertiliser nitrates are keypollutantsin theeutrophicationof water systems. Apart from its use in fertilisers and energy stores, nitrogen is a constituent of organic compounds as diverse asaramidsused in high-strength fabric andcyanoacrylateused insuperglue. Nitrogen occurs in all organisms, primarily inamino acids(and thusproteins), in thenucleic acids(DNAandRNA) and in the energy transfer moleculeadenosine triphosphate. Thehuman body containsabout 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. Thenitrogen cycledescribes the movement of the element from the air, into thebiosphereand organic compounds, then back into the atmosphere. Nitrogen is a constituent of every major pharmacological drug class, includingantibiotics. Many drugs are mimics orprodrugsof natural nitrogen-containingsignal molecules: for example, the organic nitratesnitroglycerinandnitroprussidecontrolblood pressureby metabolising intonitric oxide. Many notable nitrogen-containing drugs, such as the naturalcaffeineandmorphineor the syntheticamphetamines, act on receptors of animalneurotransmitters.