Nitrogen From Wikipedia, the free encyclopedia Nitrogen 7N ↑ N ↓ P carbon ← nitrogen → oxygen Nitrogen in the periodic table Appearance colorless gas, liquid or solid Liquid nitrogen Spectral lines of nitrogen General properties Name, symbol, number nitrogen, N, 7 Pronunciation /ˈnaɪtrədʒən/ ny-trə-jən Element category diatomic nonmetal Group, period, block 15 (pnictogens), 2, p Standard atomic weight 14.007(1) Electron configuration [He] 2s2 2p3 2, 5 Physical properties Phase gas Density (0 °C, 101.325 kPa) 1.251 g/L Liquid density at b.p. 0.808 g·cm−3 Melting point 63.15 K, −210.00 °C, −346.00 °F Boiling point 77.355 K, −195.795 °C, −320.431 °F Triple point 63.151 K, 12.52 kPa Critical point 126.192 K, 3.3958 MPa Heat of fusion (N2) 0.72 kJ·mol−1 Heat of vaporization (N2) 5.56 kJ·mol−1 Molar heat capacity (N2) 29.124 J·mol−1·K−1 Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 37 41 46 53 62 77 Atomic properties Oxidation states 5, 4, 3, 2, 1, −1, −2, −3 (strongly acidic oxide) Electronegativity 3.04 (Pauling scale) Ionization energies (more) 1st: 1402.3 kJ·mol−1 2nd: 2856 kJ·mol−1 3rd: 4578.1 kJ·mol−1 Covalent radius 71±1 pm Van der Waals radius 155 pm Miscellanea Crystal structure hexagonal Nitrogen has a hexagonal crystal structure Magnetic ordering diamagnetic Thermal conductivity 25.83 × 10−3 W·m−1·K−1 Speed of sound (gas, 27 °C) 353 m·s−1 CAS registry number 7727-37-9 History Discovery Daniel Rutherford (1772) Named by Jean-Antoine Chaptal (1790) Most stable isotopes Main article: Isotopes of nitrogen iso NA half-life DM DE (MeV) DP 13N syn 9.965 min ε 2.220 13C 14N 99.634% 14N is stable with 7 neutrons 15N 0.366% 15N is stable with 8 neutrons v t e · references Nitrogen, symbol N, is the chemical element of atomic number seven. At room temperature, it is a gas of diatomic molecules and is colorless and odorless. Nitrogen is a common element in the universe, estimated at about seventh in total abundance in our galaxy and the Solar System. On Earth, the element is primarily found as the gas molecule; it forms about 78% of Earth's atmosphere. The element nitrogen was discovered as a separable component of air, by Scottish physician Daniel Rutherford, in 1772. Many industrially important compounds, such as ammonia, nitric acid, organic nitrates (propellants and explosives), and cyanides, contain nitrogen. The extremely strong bond in elemental nitrogen dominates nitrogen chemistry, causing difficulty for both organisms and industry in converting the N 2 into useful compounds, but at the same time causing release of large amounts of often useful energy when the compounds burn, explode, or decay back into nitrogen gas. Synthetically-produced ammonia and nitrates are key industrial fertilizers and fertilizer nitrates are key pollutants in causing the eutrophication of water systems. Outside their major uses as fertilizers and energy-stores, nitrogen compounds are versatile organics. Nitrogen is part of materials as diverse as Kevlar fabric and cyanoacrylate "super" glue. Nitrogen is a constituent of molecules in every major pharmacological drug class, including the antibiotics. Many drugs are mimics or prodrugs of natural nitrogen-containing signal molecules: for example, the organic nitrates nitroglycerin and nitroprusside control blood pressure by being metabolized to natural nitric oxide. Plant alkaloids (often defense chemicals) contain nitrogen by definition, and thus many notable nitrogen-containing drugs, such as caffeine and morphine are either alkaloids or synthetic mimics that act (as many plant alkaloids do) upon receptors of animal neurotransmitters (for example, synthetic amphetamines). Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins) and also in the nucleic acids (DNA and RNA). The human body contains about 3% by mass of nitrogen, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere. Contents [hide] 1 History and etymology 2 Production 3 Properties 3.1 Isotopes 3.2 Electromagnetic spectrum 3.3 Reactions 4 Occurrence 5 Compounds 6 Applications 6.1 Nitrogen gas 6.2 Liquid nitrogen 6.3 Nitrogen compounds 7 Biological role 8 Safety 9 See also 10 Notes 11 References 12 Bibliography 13 Further reading 14 External links History and etymology[edit] Nitrogen is formally considered to have been discovered by Scottish physician Daniel Rutherford in 1772, who called it noxious air or fixed air.[1][2] The fact that there was a component of air that does not support combustion was clear to Rutherford. 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 "mephitic air" or azote, from the Greek word ἄζωτος azotos, "lifeless".[3] In it, animals died and flames were extinguished. This "mephitic air" consisted mostly of N2, but might also have included more than 1% argon. Lavoisier's name for nitrogen is used in many languages (French, Italian, Polish, Russian, Albanian, etc.) and still remains in English in the common names of many compounds, such as hydrazine and compounds of the azide ion. The English word nitrogen (1794) entered the language from the French nitrogène, coined in 1790 by French chemist Jean-Antoine Chaptal (1756–1832), from the Greek νίτρον nitron, "sodium carbonate" and the French -gène, "producing" from Greek -γενής -genes, "producer, begetter". The gas had been found in nitric acid. Chaptal's meaning was that nitrogen gas is the essential part of nitric acid, in turn formed from saltpetre (potassium nitrate), then known as nitre.[4] This word in the more ancient world originally described sodium salts that did not contain nitrate, and is a cognate of natron.[citation needed] Nitrogen compounds were well known by the Middle Ages. 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 military, industrial, and agricultural applications of nitrogen compounds used saltpetre (sodium nitrate or potassium nitrate), most notably in gunpowder, and later as fertilizer. In 1910, Lord Rayleigh discovered that an electrical discharge in nitrogen gas produced "active nitrogen", an allotrope considered to be monoatomic. The "whirling cloud of brilliant yellow light" produced by his apparatus reacted with quicksilver to produce explosive mercury nitride.[5] For a long time sources of nitrogen compounds were limited. Natural sources originated either from biology or deposits of nitrates produced by atmospheric reactions. Nitrogen fixati