Nitrogen

From Free net encyclopedia

Template:Elementbox header Template:Elementbox series Template:Elementbox groupperiodblock Template:Elementbox appearance img Template:Elementbox atomicmass gpm Template:Elementbox econfig Template:Elementbox epershell Template:Elementbox section physicalprop Template:Elementbox phase Template:Elementbox density gplstp Template:Elementbox meltingpoint Template:Elementbox boilingpoint Template:Elementbox criticalpoint Template:Elementbox heatfusion kjpmol Template:Elementbox heatvaporiz kjpmol Template:Elementbox heatcapacity jpmolkat25 Template:Elementbox vaporpressure katpa Template:Elementbox section atomicprop Template:Elementbox crystalstruct Template:Elementbox oxistates Template:Elementbox electroneg pauling Template:Elementbox ionizationenergies4 Template:Elementbox atomicradius pm Template:Elementbox atomicradiuscalc pm Template:Elementbox covalentradius pm Template:Elementbox vanderwaalsrad pm Template:Elementbox section miscellaneous Template:Elementbox magnetic Template:Elementbox thermalcond wpmkat300k Template:Elementbox speedofsound mps Template:Elementbox cas number Template:Elementbox isotopes begin Template:Elementbox isotopes decay Template:Elementbox isotopes stable Template:Elementbox isotopes stable Template:Elementbox isotopes end Template:Elementbox footer

Nitrogen is a chemical element in the periodic table which has the symbol N and atomic number 7. Commonly a colorless, odorless, tasteless and mostly inert diatomic non-metal gas, nitrogen constitutes 78 percent of Earth's atmosphere and is a constituent of all living tissues. Nitrogen forms many important compounds such as amino acids, ammonia, nitric acid, and cyanides.

Contents 1 Notable characteristics 2 Applications 2.1 Nitrogen Compounds 2.2 Molecular nitrogen (gas and liquid) 3 History 4 Occurrence 5 Compounds 6 Biological role 7 Isotopes 8 Precautions 9 See also 10 References 11 External links

Notable characteristics

Nitrogen is a non-metal, with an electronegativity of 3.0. It has five electrons in its outer shell and is therefore trivalent in most compounds. Pure nitrogen is an unreactive colorless diatomic gas at standard room temperature, and comprises 78.08% of the Earth's atmosphere. It condenses at 77 K at atmospheric pressure and freezes at 63 K. Liquid nitrogen is a common cryogen.

Applications

Nitrogen Compounds

Molecular nitrogen in the atmosphere is relatively non-reactive, but in nature it is slowly converted into biologically (and industrially) useful compounds by some living organisms, notably certain bacteria (i.e. nitrogen fixing bacteria - see Biological role below). The ability to combine or fix nitrogen is a key feature of modern industrial chemistry, where nitrogen and natural gas are converted into ammonia via the Haber process. Ammonia, in turn, can be used directly (primarily as a fertilizer), or as a precursor of many other important materials including explosives, largely via the production of nitric acid by the Ostwald process.

The salts of nitric acid include important compounds such as potassium nitrate (or saltpeter, important historically for its use in gunpowder) and ammonium nitrate, an important fertilizer. Various other nitrated organic compounds, such as nitroglycerin and trinitrotoluene, are used as explosives. Nitric acid is used as an oxidizing agent in liquid fueled rockets. Hydrazine and hydrazine derivatives find use as rocket fuels.

Molecular nitrogen (gas and liquid)

Nitrogen gas, N₂, is produced by allowing liquid nitrogen, N₂(l) (see below) to warm and evaporate. It has a wide variety of applications, including serving as a more inert replacement for air where oxidation is undesirable;

• to preserve the freshness of packaged or bulk foods (by delaying rancidity and other forms of oxidative damage)
• on top of liquid explosives for safety
• in the production of electronic parts such as transistors, diodes, and integrated circuits
• dried and pressurized, as a dielectric gas for high voltage equipment
• in the manufacture of stainless steel
• for filling automotive and aircraft tires^[1] due to its inertness and lack of moisture or oxidative qualities, as opposed to air (though this is not necessary for consumer automobiles ^[2])

Image:Nitrogen -Molecular-.JPG Contrary to some claims, nitrogen does not diffuse through tire rubber more slowly than air. Air is mostly a mixture of nitrogen and oxygen (as N₂ and O₂), and the nitrogen molecules are smaller. All else being equal, smaller molecules diffuse through porous substances more quickly.

A further example of its versatility is its use as a preferred alternative to carbon dioxide to pressurize kegs of some beers, particularly thicker stouts and Scottish and English ales, due to the smaller bubbles it produces, which make the dispensed beer smoother and headier. A modern application of a pressure sensitive nitrogen capsule known commonly as a "widget" now allows nitrogen charged beers to be packaged in cans and bottles.

Liquid nitrogen is produced industrially in large quantities by distillation from liquid air and is often referred to by the quasi-formula LN₂ (but is more accurately written N₂(l) ). It is a cryogenic (extremely cold) fluid which can cause instant frostbite on direct contact with living tissue. When appropriately insulated from ambient heat it serves as a compact and readily transported source of nitrogen gas without pressurization. Further, its ability to maintain temperatures far below the freezing point of water as it evaporates (77 K, -196 °C or -320 °F) makes it extremely useful in a wide range of applications as an open-cycle refrigerant, including;

• the immersion freezing and transportation of food products
• the cryopreservation of blood, reproductive cells (sperm and egg), and other biological samples and materials
• the cryonic preservation of humans and pets in the hope of future revival with molecular repair technology
• in the study of cryogenics
• for demonstrations in science education
• as a coolant for highly sensitive sensors and low-noise amplifiers
• in dermatology for removing unsightly or potentially malignant skin lesions such as warts and actinic keratosis
• as a cooling supplement for overclocking a central processing unit, a graphics processing unit, or another type of computer hardware

History

Nitrogen (Latin nitrum, Greek Nitron meaning "native soda", "genes", "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". This term has become the French word for "nitrogen" and later spread out to many other languages.

Compounds of nitrogen were known in the Middle Ages. The alchemists knew nitric acid as aqua fortis. The mixture of nitric and hydrochloric acids was known as aqua regia, celebrated for its ability to dissolve gold. The earliest industrial and agricultural applications of nitrogen compounds used it in the form of saltpeter (sodium- or potassium nitrate), notably in gunpowder, and much later, as fertilizer, and later still, as a chemical feedstock.

Occurrence

Nitrogen is the largest single component of the Earth's atmosphere (78.084% by volume, 75.5% by weight) and is acquired for industrial purposes by the fractional distillation of liquid air or by mechanical means of gaseous air (i.e. pressurised reverse osmosis membrane or pressure swing adsorption). Compounds that contain this element have been observed in outer space. ¹⁴Nitrogen is created as part of the fusion processes in stars. Nitrogen is a large component of animal waste (for example, guano), usually in the form of urea, uric acid, and compounds of these nitrogenous products.

Molecular nitrogen is a constituent of Titan's atmosphere and has been detected in interstellar space by David Knauth and coworkers using the Far Ultraviolet Spectroscopic Explorer.

See also Nitrate minerals, Ammonium minerals.

Compounds

The main hydride of nitrogen is ammonia (NH₃) although hydrazine (N₂H₄) is also well known. Ammonia is somewhat more basic than water, and in solution forms ammonium ions (NH₄⁺). Liquid ammonia is in fact slightly amphiprotic (acts both like a Brønsted-Lowry acid and base) and forms ammonium and amide ions (NH₂^-); both amides and nitride (N^3-) salts are known, but decompose in water. Singly and doubly substituted compounds of ammonia are called amines. Larger chains, rings and structures of nitrogen hydrides are also known but are unstable.

Other classes of nitrogen anions (negatively charged ions) are azides (N₃^-), which are linear and isoelectronic to carbon dioxide. Another molecule of the same structure is dinitrogen monoxide (N₂O), also know as laughing gas. This is one of a variety of oxides, the most prominent of which are nitrogen monoxide (NO) and nitrogen dioxide (NO₂), which both contain an unpaired electron. The latter shows some tendency to dimerize and is an important component of smog.

The more standard oxides, dinitrogen trioxide (N₂O₃) and dinitrogen pentoxide (N₂O₅), are actually fairly unstable and explosive. The corresponding acids are nitrous (HNO₂) and nitric acid (HNO₃), with the corresponding salts called nitrites and nitrates. Nitric acid is one of the few acids stronger than hydronium, and is a fairly strong oxidizing agent.

Nitrogen can also be found in organic compounds. Common nitrogen functional groups include: amines, amides, nitro groups, imines, and enamines.

See also Nitrogen compounds.

Biological role

Nitrogen is an essential part of amino and nucleic acids which makes nitrogen vital to all life. Legumes such as the soybean plant, can recover nitrogen directly from the atmosphere because their roots have nodules harboring microbes that do the actual conversion to ammonia in a process known as nitrogen fixation. The enzyme nitrogenase does this conversion. The legume subsequently converts ammonia to nitrogen oxides and amino acids to form proteins. Other plants can assimilate nitrogen in the form of nitrates. Nitrates are converted to nitrites by the enzyme nitrate reductase, and then converted to ammonia by another enzyme called nitrite reductase.

Isotopes

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 and the remaining is ¹⁵N. Of the ten isotopes produced synthetically, ¹³N has a half life of nine 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 almost always result in ¹⁵N enrichment of the substrate and depletion of the product. Although precipitation often contains subequal quantities of ammonium and nitrate, because ammonium is preferentially retained by the canopy relative to atmospheric nitrate, most of the atmospheric nitrogen that reaches the soil surface is in the form of nitrate. Soil nitrate is preferentially assimilated by tree roots relative to soil ammonium.

Precautions

Rapid release of nitrogen gas into an enclosed space can displace oxygen, and therefore represents an asphixiation hazard.

Nitrogen also dissolves in the bloodstream, and rapid decompression (particularly in the case of divers ascending too rapidly) can lead to a potentially fatal condition called the bends, when nitrogen bubbles form in the bloodstream. It can also cause nitrogen narcosis.

See also

• Nutrient
• Nitrogen cycle
• NOx
• Nitrous oxide

References

• 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

External links

Template:Commons Template:Wiktionary

• WebElements.com – Nitrogen
• It's Elemental – Nitrogen
• Schenectady County Community College – Nitrogen
• Nitrogen N2 Properties, Uses, Applications
• Computational Chemistry Wikiaf:Stikstof

ar:نيتروجين bg:Азот bs:Azot ca:Nitrogen cs:Dusík cy:Nitrogen da:Kvælstof de:Stickstoff et:Lämmastik el:Άζωτο es:Nitrógeno eo:Nitrogeno eu:Nitrogeno fa:نیتروژن fr:Azote ko:질소 hr:Dušik io:Nitro ia:Nitrogeno is:Nitur it:Azoto he:חנקן la:Nitrogenium lv:Slāpeklis lt:Azotas li:Stikstof hu:Nitrogén mk:Азот mi:Hauota nl:Stikstof ja:窒素 no:Nitrogen nn:Nitrogen pl:Azot pt:Azoto ro:Azot ru:Азот sh:Dušik simple:Nitrogen sk:Dusík sl:Dušik sr:Азот fi:Typpi sv:Kväve ta:நைட்ரஜன் th:ไนโตรเจน vi:Nitơ tr:Azot uk:Азот zh:氮