Difference between revisions of "Nitrogen" - New World Encyclopedia

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{{Elementbox_header | number=7 | symbol=N | name=nitrogen | left=[[carbon]] | right=[[oxygen]] | above=- | below=[[phosphorus|P]] | color1=#a0ffa0 | color2=green }}
 
{{Elementbox_header | number=7 | symbol=N | name=nitrogen | left=[[carbon]] | right=[[oxygen]] | above=- | below=[[phosphorus|P]] | color1=#a0ffa0 | color2=green }}
 
{{Elementbox_series | [[nonmetal]]s }}
 
{{Elementbox_series | [[nonmetal]]s }}
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{{Elementbox_isotopes_begin | isotopesof=nitrogen | color1=#a0ffa0 | color2=green }}
 
{{Elementbox_isotopes_begin | isotopesof=nitrogen | color1=#a0ffa0 | color2=green }}
 
{{Elementbox_isotopes_decay | mn=13 | sym=N
 
{{Elementbox_isotopes_decay | mn=13 | sym=N
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| na=[[synthetic radioisotope|syn]] | hl=9.965 m
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| na=[[synthetic radioisotope|syn]] | hl=9.965 m
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| dm=ε | de=2.220 | pn=13 | ps=C }}
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| dm=_ | de=2.220 | pn=13 | ps=C }}
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{{Elementbox_isotopes_stable | mn=14 | sym=N | na=99.634% | n=7 }}
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{{Elementbox_isotopes_stable | mn=14 | sym=N | na=99.634 percent | n=7 }}
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{{Elementbox_isotopes_stable | mn=15 | sym=N | na=0.366% | n=8 }}
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{{Elementbox_isotopes_stable | mn=15 | sym=N | na=0.366 percent | n=8 }}
 
{{Elementbox_isotopes_end}}
 
{{Elementbox_isotopes_end}}
 
{{Elementbox_footer | color1=#a0ffa0 | color2=green }}
 
{{Elementbox_footer | color1=#a0ffa0 | color2=green }}
  
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'''Nitrogen''' is a [[chemical element]] which has the symbol '''N''' and [[atomic number]] 7 in the [[periodic table]]. Elemental nitrogen is a colorless, odorless, tasteless and mostly [[inert]] [[diatomic]] gas at [[standard conditions]], constituting 78.08% percent of [[Earth's atmosphere]]. Nitrogen is a constituent element of all living [[tissue]]s and [[amino acids]]. Many industrially important compounds, such as [[ammonia]], [[nitric acid]], and [[cyanide]]s, contain nitrogen.
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'''Nitrogen''' (symbol '''N''', [[atomic number]] 7) is the chief constituent of the [[Earth's atmosphere]] and a vital element in all known forms of life. At ordinary temperatures and pressures, free nitrogen (unbound to any other element) is a colorless, odorless, and tasteless [[gas]]. As an inert gas, it reduces the amount of [[oxygen]] available for the oxidation of natural materials, thus restricting spontaneous combustion of flammable materials and the corrosion of [[metal|metals]]. It also protects living organisms from the toxic effects of breathing pure (or highly concentrated) oxygen. The Earth's nitrogen continually cycles through the atmosphere, biosphere, and lithosphere, effected by such processes as nitrogen fixation by bacteria, metabolic processing in living things, and decomposition of dead organic matter.
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{{toc}}
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In living organisms, nitrogen atoms are part of the molecular structures of such key substances as amino acids, proteins, and nucleic acids. In industry, nitrogen gas is used as an inert replacement for air in the packaging of foods and the manufacture of steel and electronic components. Liquid nitrogen is a [[Cryogenics|cryogen]] (low-temperature refrigerant) used for freezing and transport of food and other perishable products. Ammonia, a significant compound of nitrogen, is useful for fertilizers and for the synthesis of nitric acid and other valuable compounds. Nitric acid is an [[oxidizing agent]] used in liquid-fueled [[rocket]]s, potassium nitrate is used in gunpowder, and trinitrotoluene (TNT) is a significant explosive. In addition, nitrogen is a constituent element in every major class of drugs.
  
 
== Occurrence ==
 
== Occurrence ==
  
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Nitrogen is the largest single component of the Earth's [[Earth's atmosphere|atmosphere]]&mdash;78.084% by volume and 75.5% by weight. It appears that the most common isotope, nitrogen-14 (<sup>14</sup>N) is created as part of the nuclear fusion processes in [[star]]s.
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Nitrogen makes up 78.084 percent of the volume (and 75.5 percent of the mass) of air. Its most common isotope, nitrogen-14 (<sup>14</sup>N), appears to be created through nuclear fusion processes in [[star]]s.
  
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Compounds that contain this element have been observed by astronomers, and molecular nitrogen has been detected in [[interstellar space]]* by David Knauth and coworkers using the [[Far Ultraviolet Spectroscopic Explorer]]*. Molecular nitrogen occurs in trace amounts in the atmospheres of various planets, but it is a major constituent of [[Titan (moon)|Titan]]*, the planet [[Saturn (planet)|Saturn's]] largest moon.
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Compounds that contain this element have been observed by astronomers, and molecular nitrogen has been detected in [[interstellar space]] by David Knauth and coworkers using the [[Far Ultraviolet Spectroscopic Explorer]]. Molecular nitrogen occurs in trace amounts in the atmospheres of various planets, but it is a major constituent of [[Titan (moon)|Titan]], the planet [[Saturn (planet)|Saturn's]] largest moon.
  
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Nitrogen is present in all living organisms, as part of the molecular structures of proteins, nucleic acids, and other important substances. It is a large component of animal waste, usually in the form of [[urea]]*, [[uric acid]]*, and their derivatives.
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Nitrogen is present in all living organisms, as part of the molecular structures of proteins, nucleic acids, and other important substances. It is a large component of animal waste, usually in the form of [[urea]], [[uric acid]], and their derivatives.
  
 
== Discovery and etymology ==
 
== Discovery and etymology ==
  
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Nitrogen ([[Latin]] ''nitrum'', [[Greek language|Greek]] ''Nitron'' meaning "native soda," "genes," "forming") is formally considered to have been discovered in 1772 by the chemist [[Daniel Rutherford]]*, who knew that there was a fraction of air that did not support [[combustion]]*. He called it "noxious air" or "fixed air." 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."
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Nitrogen ([[Latin]] ''nitrum'', [[Greek language|Greek]] ''Nitron'' meaning "native soda"; ''genes'' meaning "forming") is formally considered to have been discovered in 1772 by the chemist [[Daniel Rutherford]], who knew that there was a fraction of air that did not support [[combustion]]. He called it "noxious air" or "fixed air." 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."
  
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Nitrogen gas was [[inert]]* (unreactive) enough that [[Antoine Lavoisier]] referred to it as "azote," from the [[Greek language|Greek]] word αζωτος meaning "lifeless." Animals died in it, and it was the principal component of air in which animals had suffocated and flames had burned to extinction. This term became the [[French language|French]] word for nitrogen and later spread to many other languages.
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Nitrogen gas was [[inert]] (unreactive) enough that [[Antoine Lavoisier]] referred to it as "azote," from the [[Greek language|Greek]] word αζωτος meaning "lifeless." It was the principle component of air in which animals had suffocated and flames had burned to extinction. This term became the [[French language|French]] word for nitrogen and later spread to many other languages.
  
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The [[alchemy|alchemists]] of the [[Middle Ages]] experimented with various compounds of nitrogen. For instance, they knew [[nitric acid]]* as ''aqua fortis'' (strong water). The mixture of nitric acid and [[hydrochloric acid]]* was called ''aqua regia'' (royal water), celebrated for its ability to dissolve [[gold]] (the "king" of metals). In the earliest industrial and [[Agriculture|agricultural]] applications of nitrogen compounds, [[saltpeter]]* (sodium nitrate or potassium nitrate) was used in [[gunpowder]]*, much later as [[fertilizer]], and later still as a chemical [[feedstock]]*.
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The [[alchemy|alchemists]] of the [[Middle Ages]] experimented with various compounds of nitrogen. For instance, they knew [[nitric acid]] as ''aqua fortis'' (strong water). The mixture of nitric acid and [[hydrochloric acid]] was called ''aqua regia'' (royal water), celebrated for its ability to dissolve [[gold]] (the "king" of metals). In the earliest industrial and [[Agriculture|agricultural]] applications of nitrogen compounds, [[saltpeter]] (sodium nitrate or potassium nitrate) was used in [[gunpowder]], much later as [[fertilizer]], and later still as a chemical [[feedstock]].
  
 
== Notable characteristics ==
 
== Notable characteristics ==
  
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Nitrogen is a chemical element in the [[periodic table]], situated at the top of group 15 (former group 5A), just above [[phosphorus]]. In addition, it lies in period 2, flanked by [[carbon]] and [[oxygen]]. Classified as a [[nonmetal]], it has an [[electronegativity]] of 3.0. Each atom of nitrogen has five [[electron]]s in its outer shell, and it forms three [[covalent bond]]s in most compounds.
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[[Image:Nitrogen_-Molecular-.JPG|thumb|150px|left|A computer rendering of the nitrogen molecule, N<sub>2</sub>]]
  
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Nitrogen gas consists of diatomic [[molecule]]s, each of which has the chemical formula N<sub>2</sub>. This gas [[condensation|condenses]] to the liquid form at 77 Kelvin (K) at [[atmospheric pressure]]* and freezes at 63 K. Liquid nitrogen is a common [[cryogen]] (an extremely low-temperature refrigerant).
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Nitrogen is a chemical element in the [[periodic table]], situated at the head of group 15 (former group 5A), just above [[phosphorus]]. In addition, it lies in period 2, flanked by [[carbon]] and [[oxygen]]. Classified as a [[nonmetal]], it has an [[electronegativity]] of 3.0. Each atom of nitrogen has five [[electron]]s in its outer shell, and it forms three [[covalent bond]]s in most compounds.
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Nitrogen gas consists of diatomic [[molecule]]s, each of which has the chemical formula N<sub>2</sub>. The two nitrogen atoms in each molecule are attached to each other by a strong, triple [[covalent bond]]. For this reason, nitrogen gas is extremely stable and inert.
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The gas [[condensation|condenses]] to the liquid form at 77 Kelvin (K) at [[atmospheric pressure]] and freezes at 63 K. Liquid nitrogen is a common [[cryogen]] (an extremely low-temperature refrigerant) that can cause instant [[frostbite]] on direct contact with living tissue.
  
 
=== Isotopes ===
 
=== Isotopes ===
  
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There are two stable [[isotope]]s of nitrogen: <sup>14</sup>N and <sup>15</sup>N. By far the most common is <sup>14</sup>N (99.634%), which is thought to be produced in [[star]]s by a set of nuclear fusion reactions called the "carbon-nitrogen-oxygen cycle" (CNO cycle). Of the 10 isotopes produced synthetically, <sup>13</sup>N has a [[half life]]* of nine minutes, and the remaining isotopes have half lives on the order of seconds or less.
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There are two stable [[isotope]]s of nitrogen: <sup>14</sup>N and <sup>15</sup>N. By far the most common is <sup>14</sup>N (99.634 percent), which is thought to be produced in [[star]]s by a set of nuclear fusion reactions called the "carbon-nitrogen-oxygen cycle" (CNO cycle). Of the 10 isotopes produced synthetically, <sup>13</sup>N has a [[half life]] of nine minutes, and the remaining isotopes have half lives on the order of seconds or less. In the [[Earth's atmosphere]], 0.73 percent of molecular nitrogen consists of <sup>14</sup>N<sup>15</sup>N, and almost all the rest is <sup>14</sup>N<sub>2</sub>.
  
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In the [[Earth's atmosphere]], 0.73% of molecular nitrogen consists of <sup>14</sup>N<sup>15</sup>N, and almost all the rest is <sup>14</sup>N<sub>2</sub>.
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==Biological role==
  
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==Biological role==
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Nitrogen is an essential element in the molecules of [[amino acid]]s, [[protein]]s, [[nucleic acid]]s, and other substances vital to life. Specific bacteria (such as those of the genus ''Rhizobium'') possess certain enzymes ("nitrogenases") that can fix atmospheric nitrogen (see [[nitrogen fixation]]) into a form (ammonium ion) that is chemically useful for higher organisms. This process requires a large amount of energy and anoxic ([[oxygen]]-free) conditions. Usually, these bacteria exist in a symbiotic relationship in the root nodules of leguminous plants such as clover or the soya bean plant. Nitrogen-fixing bacteria can also be symbiotic with other plant species, such as alders, lichens, casuarina, myrica, liverwort, and gunnera.
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As part of the symbiotic relationship, the plant converts the ammonium ions to nitrogen oxides and amino acids to form [[protein]]s and other biologically useful molecules, such as [[alkaloids]]. In return, the plant secretes sugars that the bacteria can use.
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Some plants can assimilate nitrogen directly in the form of nitrates, which may be present in the soil from natural mineral deposits, artificial fertilizers, animal waste, or organic decay (as the product of bacteria that are not specifically associated with the plant). Nitrates absorbed in this fashion are converted to nitrites by the enzyme nitrate reductase, and then converted to ammonia by another enzyme called nitrite reductase.
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Nitrogen compounds are basic building blocks in animal biology. Animals use nitrogen-containing amino acids from plant sources as starting materials for all nitrogen-compound animal biochemistry, including the manufacture of [[protein]]s and [[nucleic acid]]s. Many saltwater fish manufacture large amounts of [[trimethylamine oxide]] to protect them from the high osmotic effects of their environment. In animals, [[nitric oxide]] (NO) is derived from an amino acid and serves as an important regulatory molecule for circulation.
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Animal metabolism of nitrogen in proteins generally results in the excretion of [[urea]], while animal metabolism of nucleic acids results in the excretion of urea and [[uric acid]]. The characteristic odor of animal flesh decay is caused by nitrogen-containing long-chain [[amine]]s, such as [[putrescene]] and [[cadaverine]]. The decay of organisms and their waste products may produce small amounts of nitrate, but most decay processes eventually return nitrogen content to the atmosphere, as molecular nitrogen.
  
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See also [[nitrogen cycle]]
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== Industrial production ==
  
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Nitrogen is an essential part of [[amino acids]] and [[nucleic acid]]s both of which are essential to all life. Specific bacteria (e.g. Rhizobium ''trifolium'') possess [[nitrogenase]] enzymes which can fix atmospheric nitrogen (see [[nitrogen fixation]]) into a form (ammonium ion) which is chemically useful to higher organisms. This process requires a large amount of energy and anoxic conditions. Such bacteria may be free in the soil (e.g. azotobacter) but normally exist in a symbiotic relationship in the root nodules of leguminous plants (e.g. clover or the soya bean plant). Nitrogen fixating bacteria can be symbiotic with a number of unrelated plant species. Common examples are legumes, alders, lichens, casuarina, myrica, liverwort, and gunnera.  
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Nitrogen is produced industrially in large quantities by a method known as the ''fractional distillation'' of liquefied air. Isolated in the liquid form, this nitrogen is often referred to by the quasi-formula LN<sub>2</sub>, but it is more accurately written as N<sub>2</sub>''(l)''. Technologies that isolate nitrogen from gaseous air include methods known as ''pressure swing adsorption'' and ''membrane separation''. In addition, commercial nitrogen is often obtained as a byproduct of air processing during the industrial concentration of oxygen for steelmaking and other purposes. The formula for gaseous nitrogen is N<sub>2</sub>''(g)''.
  
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As part of the symbiotic relationship, the plant subsequently converts the ammonium ion to nitrogen oxides and amino acids to form [[protein]]s and other biologically useful molecules, such as [[alkaloids]]. In return, the plant secretes sugars to the symbiotic bacteria.
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== Applications of molecular nitrogen ==
  
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Some plants are able to assimilate nitrogen directly in the form of nitrates which may be present in soil from natural mineral deposits, artificial fertilizers, animal waste, or organic decay (as the product of bacteria, but not bacteria specifically associated with the plant). Nitrates absorbed in this fashion are converted to nitrites by the enzyme ''nitrate'' reductase, and then converted to ammonia by another enzyme called ''nitrite'' reductase.
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Nitrogen gas has a wide variety of applications, including serving as an inert replacement for air where [[redox|oxidation]] is undesirable. Some examples are as follows.
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* It helps preserve the freshness of packaged or bulk foods by delaying the onset of rancidity and other forms of oxidative damage.
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* It is placed on top of liquid explosives for safety.
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* It is used in the manufacture of [[electronics|electronic]] parts such as [[transistor]]s, [[diode]]s, and [[integrated circuit]]s.
  
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Nitrogen compounds are basic building blocks in animal biology. Animals use nitrogen-containing [[amino acids]] from plant sources, as starting materials for all nitrogen-compound animal biochemistry, including the manufacture of [[proteins]] and [[nucleic acids]]. Many saltwater fish manufacture large amounts of [[trimethylamine oxide]] to protect them from the high osmotic  effects of their environment (conversion of this compound to [[dimethylamine]] is responsible for the early odor in unfresh saltwater fish: PMID 15186102). In animals, the free radical molecule [[nitric oxide]] (NO), which is derived from an amino acid, serves as an important regulatory molecule for circulation.
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[[Image:Liquid nitrogen tank.JPG|thumb|150px|A tank of liquid nitrogen that supplies a cryogenic freezer (for storing laboratory samples at a temperature of about -150 °C)]]
  
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Animal metabolism of NO results in production of [[nitrite]]. Animal metabolism of nitrogen in proteins generally results in excretion of [[urea]], while animal metabolism of nucleic acids results in excretion of [[urea]] and [[uric acid]]. The characteristic odor of animal flesh decay is caused by nitrogen-containing long-chain [[amines]], such as [[putrescene]] and [[cadaverine]].
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* Dried and pressurized nitrogen is used as a [[dielectric]] gas for [[high-voltage]] equipment.
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* It is used in the manufacture of [[stainless steel]].
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* Given its inertness and lack of [[moisture]] (as opposed to air), nitrogen gas is used to fill race-car and aircraft tires, though this is not necessary for consumer automobiles.<ref>[http://auto.howstuffworks.com/question594.htm Howstuffworks: "Why don't they use normal air in race car tires"] Accessed on August 7, 2006.</ref><ref>[http://www.cartalk.com/content/columns/Archive/1997/September/05.html Car Talk: "Diffusion, moisture and tyre expansion"] Accessed on August 7, 2006.</ref>
  
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Decay of organisms and their waste products may produce small amounts of nitrate, but most decay eventually returns nitrogen content to the atmosphere, as molecular nitrogen.
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When appropriately [[Thermal insulation|insulated]] from ambient [[heat]], liquid nitrogen serves as a compact, readily transportable source of nitrogen gas without pressurization. Furthermore, its ability to maintain temperatures far below the [[freezing point]] of water as it boils at (77 [[Kelvin|K]], -196 °[[Celsius|C]] or -320 °[[Fahrenheit|F]]) makes it extremely useful in a wide range of applications as an open-cycle [[refrigerant]]. Some uses of liquid nitrogen include:
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* The immersion freezing and transportation of [[food]] products.
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* The [[cryopreservation]] of [[blood]], reproductive cells ([[sperm]] and [[Ovum|egg]]), and other [[biology|biological]] samples and materials.
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* The [[cryonics|cryonic preservation of humans and pets]] in the hope of future revival with molecular repair technology.
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* The study of [[cryogenics]].
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* Demonstrations in [[science education]].
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* As a [[coolant]], it is used for highly sensitive [[sensor]]s and low-noise [[amplifier]]s.
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* In [[dermatology]], it is used for removing unsightly or potentially [[skin cancer|malignant skin lesions]] such as [[wart]]s and [[actinic keratosis]].
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* It is a cooling medium during machining of high strength materials.
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* It is a supplement for cooling [[computer hardware]] such as a [[central processing unit]] or a [[graphics processing unit]].
  
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== Modern applications ==
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== Compounds of nitrogen ==
  
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Nitrogen gas is acquired for industrial purposes by the fractional [[distillation]] of liquid air, or by mechanical means using gaseous air (i.e. pressurised reverse [[Osmotic pressure|osmosis membrane]] or pressure swing adsorption). Commercial nitrogen is often a byproduct of air-processing for industrial concentration of oxygen for steelmaking and other purposes.
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=== Inorganic compounds ===
  
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===Molecular nitrogen (gas and liquid)===
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Nitrogen forms part of various inorganic compounds, some of which are noted below.
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Nitrogen gas has a wide variety of applications, including serving as a more [[inert]] replacement for air where [[redox|oxidation]] is undesirable;
 
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* to preserve the freshness of packaged or bulk foods (by delaying [[Rancidification|rancidity]] and other forms of oxidative damage)
 
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* on top of liquid explosives for safety
 
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* in the production of [[electronics|electronic]] parts such as [[transistor]]s, [[diode]]s, and [[integrated circuit]]s
 
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* dried and pressurized, as a [[dielectric]] gas for [[high voltage]] equipment
 
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* in the manufacture of [[stainless steel]]
 
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* for filling automotive and aircraft [[tire]]s<ref>{{cite web | url=http://auto.howstuffworks.com/question594.htm | title=Howstuffworks "Why don't they use normal air in race car tires | accessdate=2006-07-22}}</ref> due to its inertness and lack of [[moisture]] or oxidative qualities, as opposed to air, though this is not necessary for consumer automobiles.<ref>{{cite web | url=http://www.cartalk.com/content/columns/Archive/1997/September/05.html | title=Car Talk: Diffusion, moisture and tyre expansion | accessdate=2006-07-22}}</ref>
 
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[[Image:Nitrogen_-Molecular-.JPG|thumb|150px|A computer rendering of the Nitrogen Molecule, N<sub>2</sub>.]]
 
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Contrary to some claims that nitrogen will diffuse more rapidly through rubber tires than air (and oxygen), nitrogen molecules are less likely to escape from the inside of a tire compared to the traditional air mixture used. [[Earth's atmosphere|Air]] consists mostly of nitrogen and oxygen.  Nitrogen molecules are larger than oxygen molecules and therefore, all else being equal, larger molecules diffuse through porous substances slower than smaller molecules.
 
  
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A further example of its versatility is its use as a preferred alternative to [[carbon dioxide]] to pressurize kegs of some [[beer]]s, particularly thicker [[ale|stouts]] and Scottish and English [[ale]]s, 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 (beer)|widget]]" now allows nitrogen charged beers to be packaged in cans and bottles.
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'''Ammonia''': The main neutral [[hydride]] of nitrogen is [[ammonia]] (NH<sub>3</sub>), although [[hydrazine]] (N<sub>2</sub>H<sub>4</sub>) is also common. Ammonia is a chemical base&mdash; more basic than [[water]] by 6 orders of magnitude. In [[solution]], ammonia combines with protons (H<sup>+</sup> ions) to form [[ammonium]] [[Ion (physics)|ion]]s (NH<sub>4</sub><sup>+</sup>). Liquid ammonia (boiling point 240 K) is "amphiprotic"&mdash;that is, it can behave as an acid as well as a base. As an acid, it donates a proton (H<sup>+</sup>) to another molecule to form the [[amide]] ion (NH<sub>2</sub><sup>&minus;</sup>); as a base, it receives a proton (H<sup>+</sup>) from another molecule to form the ammonium ion (NH<sub>4</sub><sup>+</sup>).
  
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[[Image:Liquid nitrogen tank.JPG|thumb|150px|A tank of liquid nitrogen, used to supply a [[Cryopreservation|cryogenic freezer]] (for storing laboratory samples at a temperature of about -150 Celsius).]]
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'''Amides''': An inorganic amide is a compound in which a metal cation is combined with the amide anion (NH<sub>2</sub><sup>-</sup>) mentioned above. An example is sodium amide (NaNH<sub>2</sub>). An inorganic amide is an extremely strong base and decomposes in water. Note that [[Inorganic compound|inorganic]] amide salts are distinctly different from [[Organic compound|organic]] amide compounds mentioned below.
  
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'''Liquid nitrogen''' is produced industrially in large quantities by [[fractional distillation]] of [[liquid air]] and is often referred to by the quasi-formula '''LN<sub>2</sub>''' (but is more accurately written '''N<sub>2</sub>(''l'')''' ). It is a [[cryogenics|cryogenic]] fluid which can cause instant [[frostbite]] on direct contact with living tissue. When appropriately [[Thermal insulation|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 boils at (77 [[Kelvin|K]], -196 °[[Celsius|C]] or -320 °[[Fahrenheit|F]]) makes it extremely useful in a wide range of applications as an open-cycle [[refrigerant]], including;
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'''Nitrides''': In the molecule of a nitride compound, a nitrogen atom is attached to an atom of a more [[Electronegativity|electropositive]] element. Some nitrides, such as lithium nitride (Li<sub>3</sub>N), are salt-like, in which the nitrogen exists as an ion with three negative charges (N<sup>3&minus;</sup>). The salt-like nitrides are strong bases and readily decompose in water. Other nitrides, such as boron nitride (BN), are inert.
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* the immersion freezing and transportation of [[food]] products
 
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* the [[cryopreservation]] of [[blood]], reproductive cells ([[sperm]] and [[Ovum|egg]]), and other [[biology|biological]] samples and materials (see [[:Image:Liquid nitrogen tank.JPG|image]] at right)
 
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* the [[cryonics|cryonic preservation of humans and pets]] in the hope of future revival with molecular repair technology
 
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* in the study of [[cryogenics]]
 
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* for demonstrations in [[science education]]
 
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* as a [[coolant]] for highly sensitive [[sensor]]s and low-noise [[amplifier]]s
 
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* in [[dermatology]] for removing unsightly or potentially [[skin cancer|malignant skin lesions]] such as [[wart]]s and [[actinic keratosis]]
 
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* as a cooling supplement for [[overclocking]] a [[central processing unit]], a [[graphics processing unit]], or another type of [[computer hardware]]
 
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* as a cooling medium during machining of high strength materials.
 
  
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== Nitrogen compounds in industry ==
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'''Azides''': An inorganic azide is a salt in which a metal cation is combined with one or more azide anions (N<sub>3</sub><sup>&minus;</sup>). Each azide anion has a linear structure, N<sup>&minus;</sup>=N<sup>+</sup>=N<sup>&minus;</sup>, with a net charge of -1. Sodium azide is used in airbags, but the azide anion is toxic. Organic azides are noted below.
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===Simple compounds ===
 
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''See also the category [[:category:Nitrogen compounds|Nitrogen compounds]].''
 
  
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The main neutral [[hydride]] of nitrogen is [[ammonia]] (N[[hydrogen|H]]<sub>3</sub>), although [[hydrazine]] (N<sub>2</sub>H<sub>4</sub>) is also commonly used. Ammonia is more [[Basic (chemistry)|basic]] than [[water]] by 6 orders of magnitude. In [[solution]] ammonia forms the [[ammonium]] [[ion]] (NH<sub>4</sub><sup>+</sup>). Liquid ammonia (b.p. 240 K) is [[amphiprotic]] (displaying either [[Brønsted-Lowry]] acidic or basic character) and forms ammonium and less commonly) [[amide]] ions (NH<sub>2</sub><sup>-</sup>); both amides and [[nitride]] (N<sup>3-</sup>) [[salt]]s are known, but [[Chemical decomposition|decompose]] in water. Singly, doubly, triply and quadruply substituted alkyl compounds of ammonia are called [[amine]]s (four substitutions, to form commercially and biologically important quarternary amines, results in a positively charged nitrogen, and thus a water-soluble, or at least [[amphiphilic]], compound). Larger chains, rings and structures of nitrogen hydrides are also known, but are generally unstable.
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'''Oxides''' and '''Oxoacids''': Nitrogen forms a variety of [[oxide]]s. The most prominent ones are [[nitrogen monoxide]] (NO) (known more commonly as [[nitric oxide]] in biology) and [[nitrogen dioxide]] (NO<sub>2</sub>). Both types of molecules contain an unpaired [[electron]]. The latter shows some tendency to form dimers and is a significant component of [[smog]]. In addition, nitrogen forms dinitrogen monoxide (or nitrous oxide) (N<sub>2</sub>[[oxygen|O]]), which is also known as laughing gas. The more standard oxides, [[dinitrogen trioxide]] (N<sub>2</sub>O<sub>3</sub>) and [[dinitrogen pentoxide]] (N<sub>2</sub>O<sub>5</sub>), are fairly unstable and explosive. The corresponding acids (oxoacids, or oxygen-containing acids) are '''nitrous acid''' (HNO<sub>2</sub>) and '''[[nitric acid]]''' (HNO<sub>3</sub>), and the corresponding salts are called '''nitrites''' and '''nitrates'''.
  
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Other classes of nitrogen [[anion]]s (negatively charged ions) are [[azide]]s (N<sub>3</sub><sup>-</sup>), which are linear and [[isoelectronic]] to [[carbon dioxide]]. Another [[molecule]] of the same structure is [[Nitrous oxide|dinitrogen monoxide]] (N<sub>2</sub>[[oxygen|O]]), also known as laughing gas. This is one of a variety of [[oxide]]s, the most prominent of which are [[nitrogen monoxide]] (NO) (known more commonly as [[nitric oxide]] in biology) and [[nitrogen dioxide]] (NO<sub>2</sub>), which both contain an unpaired [[electron]]. The latter shows some tendency to [[dimerize]] and is an important component of [[smog]].
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=== Organic compounds ===
  
−
The more standard oxides, [[dinitrogen trioxide]] (N<sub>2</sub>O<sub>3</sub>) and [[dinitrogen pentoxide]] (N<sub>2</sub>O<sub>5</sub>), are actually fairly unstable and explosive. The corresponding acids are [[nitrous acid|nitrous]] (HNO<sub>2</sub>) and [[nitric acid]] (HNO<sub>3</sub>), with the corresponding salts called [[nitrite]]s and [[nitrate]]s. Nitric acid is one of the few acids stronger than [[hydronium]], and is a fairly strong [[oxidizing agent]].
+
Nitrogen is also an important element in many [[organic compound]]s, in which it is directly bound to one or more carbon atoms. Some examples are given below.
 +
* '''Amines''': Between one and four carbon-containing groups ("alkyl" or "aryl" groups) are attached to a nitrogen atom, and the corresponding products are known as primary, secondary, tertiary, and quarternary amines. Many amines are commercially and biologically important compounds.
 +
* '''Amides''': In an organic amide, a "carbonyl" group (C=O) is directly attached to a nitrogen atom, and the bond is called an "amide bond." The general chemical formula of an organic amide is R<sub>1</sub>(CO)NR<sub>2</sub>R<sub>3</sub>, where R<sub>2</sub> or R<sub>3</sub> or both may represent a hydrogen atom (each). A peptide or protein consists of a chain of amino acids linked to one another through amide bonds.
 +
* '''Nitro compounds''': The nitro compounds are organic compounds containing one or more "nitro" (-NO<sub>2</sub>) functional groups attached directly to carbon atoms. Many of these compounds are highly explosive. Examples are trinitrotoluene (TNT) and trinitrophenol (picric acid).
 +
* '''Azides''': An organic azide is an organic compound in which the functional group N<sub>3</sub> is directly attached to a carbon atom.
 +
* '''Imines''': An imine is a compound containing a carbon-nitrogen double bond. The general formula may be written as R<sub>1</sub>R<sub>2</sub>C=NR<sub>3</sub>. When the imine is made to react with hydrogen, it is converted to the amine.
  
−
Nitrogen can also be found in [[organic compound]]s. Common nitrogen [[functional group]]s include: [[amines]], [[amides]], [[nitro]] groups, [[imine]]s, and [[enamine]]s. The amount of nitrogen in a [[chemical substance]] can be determined by the [[Kjeldahl method]].
+
== Applications of nitrogen compounds ==
  
−
===Nitrogen compounds of notable economic importance===
+
The ability to combine or "fix" molecular nitrogen is a key feature of modern industrial chemistry, where nitrogen and hydrogen are made to react to form ammonia, by what is called the ''Haber process''. Ammonia, in turn, can be used directly as a [[fertilizer]] and in the synthesis of nitrated fertilizers, or it can be used as a precursor of many other important materials, largely through the production of [[nitric acid]] by the ''Ostwald process''.
−
Molecular nitrogen in the atmosphere is relatively non-reactive due to its strong bond, and the (N<sub>2</sub>) plays an inert role in the human body, being neither produced or destroyed. In nature, nitrogen is slowly converted into biologically (and industrially) useful compounds by some living organisms, notably certain [[bacteria]] (i.e. [[nitrogen fixing bacteria]] - see ''[[#Biological role|Biological role]]'' above). Molecular nitrogen is also released into the atmosphere in the process of decay, in dead plant and animal tissues. The ability to combine or '''fix''' molecular 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]], and in the synthesis of nitrated fertilizers), or as a precursor of many other important materials including [[explosives]], largely via the production of [[nitric acid]] by the [[Ostwald process]].
 
  
−
The [[salt]]s 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 and explosive (see [[ANFO]]). Various other nitrated organic compounds, such as [[nitroglycerin]] and [[trinitrotoluene]], and [[nitrocellulose]], are used as explosives and propellants for modern firearms. Nitric acid is used as an [[oxidizing agent]] in liquid fueled [[rocket]]s. [[Hydrazine]] and hydrazine derivatives find use as rocket [[fuel]]s. In all of these compounds, the basic instability and tendency to burn or explode is derived from the fact that nitrogen is present as an oxide, and not as the far more stable nitrogen molecule (N<sub>2</sub>) which is a product of the compound's decomposition. When nitrates burn or explode, the formation of the powerful triple bond in the (N<sub>2</sub>) which results, produces most of the energy of the reaction.
+
The [[salt]]s 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 and explosive. Various other nitrated organic compounds, such as [[nitroglycerin]], [[trinitrotoluene]], and [[nitrocellulose]], are used as explosives and propellants for modern firearms. Nitric acid is used as an [[oxidizing agent]] in liquid fueled [[rocket]]s. [[Hydrazine]] and its derivatives find use as rocket [[fuel]]s. For all these compounds, the basic instability and tendency to burn or explode is derived from the fact that nitrogen is present as an oxide, and not as the far more stable nitrogen molecule (N<sub>2</sub>). When nitrates burn or explode, the formation of the powerful triple bond in the resultant (N<sub>2</sub>) generates most of the energy of the reaction.
  
−
Nitrogen is a constituent of molecules in every major drug class in pharmacology and medicine. [[Nitrous oxide]] (N<sub>2</sub>0) was discovered early in the 19th century to be a partial anesthetic, though it was not used as a surgical anesthetic until later. Called "[[laughing gas]]", it was found capable of inducing a state of social disinhibition resembling drunkenness. Other notable nitrogen-containing drugs are drugs derived from plant [[alkaloids]], such as [[morphine]] (there exist many alkaloids known to have pharmacological effects; in some cases they appear natural chemical defences of plants against predation). Nitrogen containing drugs include all of the major classes of antibiotics, and organic nitrate drugs like [[nitroglycerin]] and [[nitroprusside]] which regulate blood pressure and heart action by mimicing the action of [[nitric oxide]].
+
In medicine, nitrogen is a constituent of molecules in every major drug class. Nitrous oxide (N<sub>2</sub>0) was discovered early in the nineteenth century to be a partial anesthetic, though it was not used as a surgical anesthetic until later. Called "laughing gas," it was found capable of inducing a state of social disinhibition resembling drunkenness. Other notable nitrogen-containing drugs, such as [[morphine]], are derived from plant [[alkaloids]]. Many alkaloids are known to have pharmacological effects, and some of them may play a role in the plants' natural defenses against predation. Organic nitro drugs, such as [[nitroglycerin]] and [[nitroprusside]], help reduce blood pressure by widening blood vessels.
  
 
== Precautions ==
 
== Precautions ==
−
Rapid release of nitrogen gas into an enclosed space can displace oxygen, and therefore represents an [[asphyxiation]] hazard.  An example occurred shortly before the launch of the first Space Shuttle mission in [[1981]], when two technicians were killed in a space located in the Shuttle's [[Mobile Launch Platform]] that was pressurized with pure nitrogen as a precaution against fire.
 
  
−
When breathed at high [[partial pressures]] (more than about 3 atmospheres, encountered a depths below about 30 m in diving) nitrogen begins to act as an anesthetic agent. As such, it can cause [[nitrogen narcosis]], a temporary semi-anesthetized condition of mental impairment similar to that caused by [[nitrous oxide]].
+
Rapid release of nitrogen gas into an enclosed space can displace oxygen, thus representing an asphyxiation hazard. Shortly before the launch of the first [[Space Shuttle]] mission in 1981, two technicians were killed in an area in the Shuttle's [[Mobile Launch Platform]] that was pressurized with pure nitrogen as a precaution against fire.
 +
 
 +
When breathed at high [[partial pressures]] (higher than 3 atmospheres, encountered at diving depths below about 30 meters) nitrogen begins to act as an anesthetic agent. As such, it can cause [[nitrogen narcosis]]&mdash;a temporary, semi-anesthetized condition of mental impairment similar to that caused by [[nitrous oxide]].
  
−
Nitrogen also dissolves in the [[Cardiovascular system|bloodstream]], and rapid decompression (particularly in the case of divers ascending too quickly, or astronauts decompressing too quickly from cabin pressure to spacesuit pressure) can lead to a potentially fatal condition called [[decompression sickness]] (formerly known as caisson sickness or more commonly, the "bends"), when nitrogen bubbles form in the bloodstream.  
+
Nitrogen also dissolves in the bloodstream. When divers ascend too quickly, or astronauts decompress too quickly from cabin pressure to spacesuit pressure, the rapid decompression can lead to a potentially fatal condition called "decompression sickness"&mdash;formerly known as "caisson sickness" or the "bends"&mdash;when nitrogen bubbles form in the bloodstream.
  
−
Direct skin contact with liquid nitrogen causes severe frostbite (cryogenic burns) within moments to seconds, depending on form of liquid nitrogen (liquid vs. mist) and surface area of the nitrogen-soaked material (soaked clothing or cotton causing more rapid damage than a spill of direct liquid to skin, which for a few seconds is protected by the [[Leidenfrost effect]] ).
+
Direct skin contact with liquid nitrogen causes severe frostbite (cryogenic burns) within seconds, depending on the form of liquid nitrogen (liquid versus mist) and surface area of the nitrogen-soaked material.
  
 
== See also ==
 
== See also ==
 +
 +
* [[Earth's atmosphere]]
 
* [[Nutrient]]
 
* [[Nutrient]]
 
* [[Nitrogen cycle]]
 
* [[Nitrogen cycle]]
−
* [[NOx]]
+
 
−
* [[Nitrous oxide]]
+
== Notes ==
 +
<references />
  
 
== References ==
 
== References ==
−
<references />
+
 
 
*[http://periodic.lanl.gov/elements/7.html Los Alamos National Laboratory &ndash; Nitrogen]
 
*[http://periodic.lanl.gov/elements/7.html Los Alamos National Laboratory &ndash; Nitrogen]
−
* ''Chemistry of the Elements'', N. N. Greenwood and A. Earnshaw. ISBN 0-08-022057-6
+
* Garrett, R. H. and C. M. Grisham. ''Biochemistry''. Second edition, 1999. ISBN 0030223180
−
* ''Biochemistry'', R.H. Garrett and C.M. Grisham. 2nd edition, 1999. ISBN 0-03-022318-0
+
* Greenwood, N. N. and A. Earnshaw. ''Chemistry of the Elements''. ISBN 0080220576
  
 
== External links ==
 
== External links ==
−
 
+
All links retrieved November 15, 2022.
−
* [http://www.newton.dep.anl.gov/askasci/chem99/chem99306.htm Why high nitrogen density in explosives?]
 
 
* [http://www.webelements.com/webelements/elements/text/N/index.html WebElements.com &ndash; Nitrogen]
 
* [http://www.webelements.com/webelements/elements/text/N/index.html WebElements.com &ndash; Nitrogen]
 
* [http://education.jlab.org/itselemental/ele007.html It's Elemental &ndash; Nitrogen]
 
* [http://education.jlab.org/itselemental/ele007.html It's Elemental &ndash; Nitrogen]
−
* [http://www.sunysccc.edu/academic/mst/ptable/n.html Schenectady County Community College &ndash; Nitrogen]
 
 
* [http://www.uigi.com/nitrogen.html Nitrogen N2 Properties, Uses, Applications]
 
* [http://www.uigi.com/nitrogen.html Nitrogen N2 Properties, Uses, Applications]
−
* [http://box27.bluehost.com/~edsanvil/wiki/index.php?title=Nitrogen_gas Computational Chemistry Wiki]
 
−
* [http://www.2spi.com/catalog/instruments/nitrodew-supp.html Handling procedures for liquid nitrogen]
 
  
 
{{E number infobox 930-949}}
 
{{E number infobox 930-949}}

Latest revision as of 02:26, 16 November 2022

7 carbon ← nitrogen → oxygen
-
↑
N
↓
P
N-TableImage.png
periodic table
General
Name, Symbol, Number nitrogen, N, 7
Chemical series nonmetals
Group, Period, Block 15, 2, p
Appearance colorless
N,7.jpg
Atomic mass 14.0067(2) g/mol
Electron configuration 1s2 2s2 2p3
Electrons per shell 2, 5
Physical properties
Phase gas
Density (0 °C, 101.325 kPa)
1.251 g/L
Melting point 63.15 K
(-210.00 °C, -346.00 °F)
Boiling point 77.36 K
(-195.79 °C, -320.42 °F)
Critical point 126.21 K, 3.39 MPa
Heat of fusion (N2) 0.720 kJ/mol
Heat of vaporization (N2) 5.57 kJ/mol
Heat capacity (25 °C) (N2)
29.124 J/(mol·K)
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 37 41 46 53 62 77
Atomic properties
Crystal structure hexagonal
Oxidation states ±3, 5, 4, 2
(strongly acidic oxide)
Electronegativity 3.04 (Pauling scale)
Ionization energies
(more) 		1st: 1402.3 kJ/mol
2nd: 2856 kJ/mol
3rd: 4578.1 kJ/mol
Atomic radius 65 pm
Atomic radius (calc.) 56 pm
Covalent radius 75 pm
Van der Waals radius 155 pm
Miscellaneous
Magnetic ordering no data
Thermal conductivity (300 K) 25.83 mW/(m·K)
Speed of sound (gas, 27 °C) 353 m/s
CAS registry number 7727-37-9
Notable isotopes
Main article: Isotopes of nitrogen
iso NA half-life DM DE (MeV) DP
13N syn 9.965 m _ 2.220 13C
14N 99.634 percent N is stable with 7 neutrons
15N 0.366 percent N is stable with 8 neutrons

Nitrogen (symbol N, atomic number 7) is the chief constituent of the Earth's atmosphere and a vital element in all known forms of life. At ordinary temperatures and pressures, free nitrogen (unbound to any other element) is a colorless, odorless, and tasteless gas. As an inert gas, it reduces the amount of oxygen available for the oxidation of natural materials, thus restricting spontaneous combustion of flammable materials and the corrosion of metals. It also protects living organisms from the toxic effects of breathing pure (or highly concentrated) oxygen. The Earth's nitrogen continually cycles through the atmosphere, biosphere, and lithosphere, effected by such processes as nitrogen fixation by bacteria, metabolic processing in living things, and decomposition of dead organic matter.

In living organisms, nitrogen atoms are part of the molecular structures of such key substances as amino acids, proteins, and nucleic acids. In industry, nitrogen gas is used as an inert replacement for air in the packaging of foods and the manufacture of steel and electronic components. Liquid nitrogen is a cryogen (low-temperature refrigerant) used for freezing and transport of food and other perishable products. Ammonia, a significant compound of nitrogen, is useful for fertilizers and for the synthesis of nitric acid and other valuable compounds. Nitric acid is an oxidizing agent used in liquid-fueled rockets, potassium nitrate is used in gunpowder, and trinitrotoluene (TNT) is a significant explosive. In addition, nitrogen is a constituent element in every major class of drugs.

Occurrence

Nitrogen makes up 78.084 percent of the volume (and 75.5 percent of the mass) of air. Its most common isotope, nitrogen-14 (14N), appears to be created through nuclear fusion processes in stars.

Compounds that contain this element have been observed by astronomers, and molecular nitrogen has been detected in interstellar space by David Knauth and coworkers using the Far Ultraviolet Spectroscopic Explorer. Molecular nitrogen occurs in trace amounts in the atmospheres of various planets, but it is a major constituent of Titan, the planet Saturn's largest moon.

Nitrogen is present in all living organisms, as part of the molecular structures of proteins, nucleic acids, and other important substances. It is a large component of animal waste, usually in the form of urea, uric acid, and their derivatives.

Discovery and etymology

Nitrogen (Latin nitrum, Greek Nitron meaning "native soda"; genes meaning "forming") is formally considered to have been discovered in 1772 by the chemist Daniel Rutherford, who knew that there was a fraction of air that did not support combustion. He called it "noxious air" or "fixed air." 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 (unreactive) enough that Antoine Lavoisier referred to it as "azote," from the Greek word αζωτος meaning "lifeless." It was the principle component of air in which animals had suffocated and flames had burned to extinction. This term became the French word for nitrogen and later spread to many other languages.

The alchemists of the Middle Ages experimented with various compounds of nitrogen. For instance, they knew nitric acid as aqua fortis (strong water). The mixture of nitric acid and hydrochloric acid was called aqua regia (royal water), celebrated for its ability to dissolve gold (the "king" of metals). In the earliest industrial and agricultural applications of nitrogen compounds, saltpeter (sodium nitrate or potassium nitrate) was used in gunpowder, much later as fertilizer, and later still as a chemical feedstock.

Notable characteristics

A computer rendering of the nitrogen molecule, N2

Nitrogen is a chemical element in the periodic table, situated at the head of group 15 (former group 5A), just above phosphorus. In addition, it lies in period 2, flanked by carbon and oxygen. Classified as a nonmetal, it has an electronegativity of 3.0. Each atom of nitrogen has five electrons in its outer shell, and it forms three covalent bonds in most compounds.

Nitrogen gas consists of diatomic molecules, each of which has the chemical formula N2. The two nitrogen atoms in each molecule are attached to each other by a strong, triple covalent bond. For this reason, nitrogen gas is extremely stable and inert.

The gas condenses to the liquid form at 77 Kelvin (K) at atmospheric pressure and freezes at 63 K. Liquid nitrogen is a common cryogen (an extremely low-temperature refrigerant) that can cause instant frostbite on direct contact with living tissue.

Isotopes

There are two stable isotopes of nitrogen: 14N and 15N. By far the most common is 14N (99.634 percent), which is thought to be produced in stars by a set of nuclear fusion reactions called the "carbon-nitrogen-oxygen cycle" (CNO cycle). Of the 10 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. In the Earth's atmosphere, 0.73 percent of molecular nitrogen consists of 14N15N, and almost all the rest is 14N2.

Biological role

Nitrogen is an essential element in the molecules of amino acids, proteins, nucleic acids, and other substances vital to life. Specific bacteria (such as those of the genus Rhizobium) possess certain enzymes ("nitrogenases") that can fix atmospheric nitrogen (see nitrogen fixation) into a form (ammonium ion) that is chemically useful for higher organisms. This process requires a large amount of energy and anoxic (oxygen-free) conditions. Usually, these bacteria exist in a symbiotic relationship in the root nodules of leguminous plants such as clover or the soya bean plant. Nitrogen-fixing bacteria can also be symbiotic with other plant species, such as alders, lichens, casuarina, myrica, liverwort, and gunnera.

As part of the symbiotic relationship, the plant converts the ammonium ions to nitrogen oxides and amino acids to form proteins and other biologically useful molecules, such as alkaloids. In return, the plant secretes sugars that the bacteria can use.

Some plants can assimilate nitrogen directly in the form of nitrates, which may be present in the soil from natural mineral deposits, artificial fertilizers, animal waste, or organic decay (as the product of bacteria that are not specifically associated with the plant). Nitrates absorbed in this fashion are converted to nitrites by the enzyme nitrate reductase, and then converted to ammonia by another enzyme called nitrite reductase.

Nitrogen compounds are basic building blocks in animal biology. Animals use nitrogen-containing amino acids from plant sources as starting materials for all nitrogen-compound animal biochemistry, including the manufacture of proteins and nucleic acids. Many saltwater fish manufacture large amounts of trimethylamine oxide to protect them from the high osmotic effects of their environment. In animals, nitric oxide (NO) is derived from an amino acid and serves as an important regulatory molecule for circulation.

Animal metabolism of nitrogen in proteins generally results in the excretion of urea, while animal metabolism of nucleic acids results in the excretion of urea and uric acid. The characteristic odor of animal flesh decay is caused by nitrogen-containing long-chain amines, such as putrescene and cadaverine. The decay of organisms and their waste products may produce small amounts of nitrate, but most decay processes eventually return nitrogen content to the atmosphere, as molecular nitrogen.

Industrial production

Nitrogen is produced industrially in large quantities by a method known as the fractional distillation of liquefied air. Isolated in the liquid form, this nitrogen is often referred to by the quasi-formula LN2, but it is more accurately written as N2(l). Technologies that isolate nitrogen from gaseous air include methods known as pressure swing adsorption and membrane separation. In addition, commercial nitrogen is often obtained as a byproduct of air processing during the industrial concentration of oxygen for steelmaking and other purposes. The formula for gaseous nitrogen is N2(g).

Applications of molecular nitrogen

Nitrogen gas has a wide variety of applications, including serving as an inert replacement for air where oxidation is undesirable. Some examples are as follows.

  • It helps preserve the freshness of packaged or bulk foods by delaying the onset of rancidity and other forms of oxidative damage.
  • It is placed on top of liquid explosives for safety.
  • It is used in the manufacture of electronic parts such as transistors, diodes, and integrated circuits.
A tank of liquid nitrogen that supplies a cryogenic freezer (for storing laboratory samples at a temperature of about -150 °C)
  • Dried and pressurized nitrogen is used as a dielectric gas for high-voltage equipment.
  • It is used in the manufacture of stainless steel.
  • Given its inertness and lack of moisture (as opposed to air), nitrogen gas is used to fill race-car and aircraft tires, though this is not necessary for consumer automobiles.[1][2]

When appropriately insulated from ambient heat, liquid nitrogen serves as a compact, readily transportable source of nitrogen gas without pressurization. Furthermore, its ability to maintain temperatures far below the freezing point of water as it boils at (77 K, -196 °C or -320 °F) makes it extremely useful in a wide range of applications as an open-cycle refrigerant. Some uses of liquid nitrogen include:

  • 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.
  • The study of cryogenics.
  • Demonstrations in science education.
  • As a coolant, it is used for highly sensitive sensors and low-noise amplifiers.
  • In dermatology, it is used for removing unsightly or potentially malignant skin lesions such as warts and actinic keratosis.
  • It is a cooling medium during machining of high strength materials.
  • It is a supplement for cooling computer hardware such as a central processing unit or a graphics processing unit.

Compounds of nitrogen

Inorganic compounds

Nitrogen forms part of various inorganic compounds, some of which are noted below.

Ammonia: The main neutral hydride of nitrogen is ammonia (NH3), although hydrazine (N2H4) is also common. Ammonia is a chemical base— more basic than water by 6 orders of magnitude. In solution, ammonia combines with protons (H+ ions) to form ammonium ions (NH4+). Liquid ammonia (boiling point 240 K) is "amphiprotic"—that is, it can behave as an acid as well as a base. As an acid, it donates a proton (H+) to another molecule to form the amide ion (NH2−); as a base, it receives a proton (H+) from another molecule to form the ammonium ion (NH4+).

Amides: An inorganic amide is a compound in which a metal cation is combined with the amide anion (NH2-) mentioned above. An example is sodium amide (NaNH2). An inorganic amide is an extremely strong base and decomposes in water. Note that inorganic amide salts are distinctly different from organic amide compounds mentioned below.

Nitrides: In the molecule of a nitride compound, a nitrogen atom is attached to an atom of a more electropositive element. Some nitrides, such as lithium nitride (Li3N), are salt-like, in which the nitrogen exists as an ion with three negative charges (N3−). The salt-like nitrides are strong bases and readily decompose in water. Other nitrides, such as boron nitride (BN), are inert.

Azides: An inorganic azide is a salt in which a metal cation is combined with one or more azide anions (N3−). Each azide anion has a linear structure, N−=N+=N−, with a net charge of -1. Sodium azide is used in airbags, but the azide anion is toxic. Organic azides are noted below.

Oxides and Oxoacids: Nitrogen forms a variety of oxides. The most prominent ones are nitrogen monoxide (NO) (known more commonly as nitric oxide in biology) and nitrogen dioxide (NO2). Both types of molecules contain an unpaired electron. The latter shows some tendency to form dimers and is a significant component of smog. In addition, nitrogen forms dinitrogen monoxide (or nitrous oxide) (N2O), which is also known as laughing gas. The more standard oxides, dinitrogen trioxide (N2O3) and dinitrogen pentoxide (N2O5), are fairly unstable and explosive. The corresponding acids (oxoacids, or oxygen-containing acids) are nitrous acid (HNO2) and nitric acid (HNO3), and the corresponding salts are called nitrites and nitrates.

Organic compounds

Nitrogen is also an important element in many organic compounds, in which it is directly bound to one or more carbon atoms. Some examples are given below.

  • Amines: Between one and four carbon-containing groups ("alkyl" or "aryl" groups) are attached to a nitrogen atom, and the corresponding products are known as primary, secondary, tertiary, and quarternary amines. Many amines are commercially and biologically important compounds.
  • Amides: In an organic amide, a "carbonyl" group (C=O) is directly attached to a nitrogen atom, and the bond is called an "amide bond." The general chemical formula of an organic amide is R1(CO)NR2R3, where R2 or R3 or both may represent a hydrogen atom (each). A peptide or protein consists of a chain of amino acids linked to one another through amide bonds.
  • Nitro compounds: The nitro compounds are organic compounds containing one or more "nitro" (-NO2) functional groups attached directly to carbon atoms. Many of these compounds are highly explosive. Examples are trinitrotoluene (TNT) and trinitrophenol (picric acid).
  • Azides: An organic azide is an organic compound in which the functional group N3 is directly attached to a carbon atom.
  • Imines: An imine is a compound containing a carbon-nitrogen double bond. The general formula may be written as R1R2C=NR3. When the imine is made to react with hydrogen, it is converted to the amine.

Applications of nitrogen compounds

The ability to combine or "fix" molecular nitrogen is a key feature of modern industrial chemistry, where nitrogen and hydrogen are made to react to form ammonia, by what is called the Haber process. Ammonia, in turn, can be used directly as a fertilizer and in the synthesis of nitrated fertilizers, or it can be used as a precursor of many other important materials, largely through 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 and explosive. Various other nitrated organic compounds, such as nitroglycerin, trinitrotoluene, and nitrocellulose, are used as explosives and propellants for modern firearms. Nitric acid is used as an oxidizing agent in liquid fueled rockets. Hydrazine and its derivatives find use as rocket fuels. For all these compounds, the basic instability and tendency to burn or explode is derived from the fact that nitrogen is present as an oxide, and not as the far more stable nitrogen molecule (N2). When nitrates burn or explode, the formation of the powerful triple bond in the resultant (N2) generates most of the energy of the reaction.

In medicine, nitrogen is a constituent of molecules in every major drug class. Nitrous oxide (N20) was discovered early in the nineteenth century to be a partial anesthetic, though it was not used as a surgical anesthetic until later. Called "laughing gas," it was found capable of inducing a state of social disinhibition resembling drunkenness. Other notable nitrogen-containing drugs, such as morphine, are derived from plant alkaloids. Many alkaloids are known to have pharmacological effects, and some of them may play a role in the plants' natural defenses against predation. Organic nitro drugs, such as nitroglycerin and nitroprusside, help reduce blood pressure by widening blood vessels.

Precautions

Rapid release of nitrogen gas into an enclosed space can displace oxygen, thus representing an asphyxiation hazard. Shortly before the launch of the first Space Shuttle mission in 1981, two technicians were killed in an area in the Shuttle's Mobile Launch Platform that was pressurized with pure nitrogen as a precaution against fire.

When breathed at high partial pressures (higher than 3 atmospheres, encountered at diving depths below about 30 meters) nitrogen begins to act as an anesthetic agent. As such, it can cause nitrogen narcosis—a temporary, semi-anesthetized condition of mental impairment similar to that caused by nitrous oxide.

Nitrogen also dissolves in the bloodstream. When divers ascend too quickly, or astronauts decompress too quickly from cabin pressure to spacesuit pressure, the rapid decompression can lead to a potentially fatal condition called "decompression sickness"—formerly known as "caisson sickness" or the "bends"—when nitrogen bubbles form in the bloodstream.

Direct skin contact with liquid nitrogen causes severe frostbite (cryogenic burns) within seconds, depending on the form of liquid nitrogen (liquid versus mist) and surface area of the nitrogen-soaked material.

See also

Notes

  1. ↑ Howstuffworks: "Why don't they use normal air in race car tires" Accessed on August 7, 2006.
  2. ↑ Car Talk: "Diffusion, moisture and tyre expansion" Accessed on August 7, 2006.

References
ISBN links support NWE through referral fees

External links

All links retrieved November 15, 2022.


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Argon (E938) • Helium (E939) • Dichlorodifluoromethane (E940) • Nitrogen (E941) • Nitrous oxide (E942) • Butane (E943a) • Isobutane (E943b) • Propane (E944) • Oxygen (E948) • Hydrogen (E949)

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