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Nitrogen oxide

Nitrogen oxide

Overview
Nitrogen oxide can refer to a binary compound
Binary compound
A binary compound is a chemical compound that contains exactly two different elements. Examples of binary ionic compounds include calcium chloride , sodium fluoride , and magnesium oxide , whilst examples of binary covalent compounds include water , carbon monoxide , and sulfur hexafluoride...

 of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 and nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

, or a mixture of such compounds:
  • Nitric oxide
    Nitric oxide
    Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...

    , also known as nitrogen monoxide, (NO), nitrogen(II) oxide
  • Nitrogen dioxide
    Nitrogen dioxide
    Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...

     (NO2), nitrogen(IV) oxide
  • Nitrous oxide
    Nitrous oxide
    Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...

     (N2O), nitrogen(I) oxide
  • Nitrosylazide
    Nitrosylazide
    Nitrosylazide is a highly unstable nitrogen oxide, chemical formula N4O, which can be synthesized via the following reaction at low temperatures:...

     (N4O), nitrogen(I) oxide + diatomic nitrogen
    Nitrogen
    Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

  • Nitrate radical (NO3), nitrogen(VI) oxide
  • Dinitrogen trioxide
    Dinitrogen trioxide
    Dinitrogen trioxide is the chemical compound with the formula N2O3. This deep blue liquid is one of binary nitrogen oxides. It forms upon mixing equal parts of nitric oxide and nitrogen dioxide and cooling the mixture below −21 °C :Dinitrogen trioxide is only isolable at low...

     (N2O3), nitrogen(II,IV) oxide
  • Dinitrogen tetroxide
    Dinitrogen tetroxide
    Dinitrogen tetroxide is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium mixture with nitrogen dioxide; some call this mixture dinitrogen tetroxide, while some call it nitrogen dioxide.Dinitrogen tetroxide is a powerful oxidizer, making it highly...

     (N2O4), nitrogen(IV) oxide
  • Dinitrogen pentoxide
    Dinitrogen pentoxide
    Dinitrogen pentoxide is the chemical compound with the formula N2O5. Also known as nitrogen pentoxide, N2O5 is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen...

     (N2O5), nitrogen(V) oxide
  • Trinitramide
    Trinitramide
    Trinitramide is a compound of nitrogen and oxygen with the molecular formula N3. The compound was detected and described in 2010 by researchers at the Royal Institute of Technology in Sweden....

     (N(NO2)3)


In atmospheric chemistry
Atmospheric chemistry
Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary field of research and draws on environmental chemistry, physics, meteorology, computer modeling, oceanography, geology and...

 and air pollution
Air pollution
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....

 and related fields, nitrogen oxides refers specifically to NOx (NO and NO2).

Only the first three of these compounds can be isolated at room temperature.
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Encyclopedia
Nitrogen oxide can refer to a binary compound
Binary compound
A binary compound is a chemical compound that contains exactly two different elements. Examples of binary ionic compounds include calcium chloride , sodium fluoride , and magnesium oxide , whilst examples of binary covalent compounds include water , carbon monoxide , and sulfur hexafluoride...

 of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 and nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

, or a mixture of such compounds:
  • Nitric oxide
    Nitric oxide
    Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...

    , also known as nitrogen monoxide, (NO), nitrogen(II) oxide
  • Nitrogen dioxide
    Nitrogen dioxide
    Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...

     (NO2), nitrogen(IV) oxide
  • Nitrous oxide
    Nitrous oxide
    Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...

     (N2O), nitrogen(I) oxide
  • Nitrosylazide
    Nitrosylazide
    Nitrosylazide is a highly unstable nitrogen oxide, chemical formula N4O, which can be synthesized via the following reaction at low temperatures:...

     (N4O), nitrogen(I) oxide + diatomic nitrogen
    Nitrogen
    Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

  • Nitrate radical (NO3), nitrogen(VI) oxide
  • Dinitrogen trioxide
    Dinitrogen trioxide
    Dinitrogen trioxide is the chemical compound with the formula N2O3. This deep blue liquid is one of binary nitrogen oxides. It forms upon mixing equal parts of nitric oxide and nitrogen dioxide and cooling the mixture below −21 °C :Dinitrogen trioxide is only isolable at low...

     (N2O3), nitrogen(II,IV) oxide
  • Dinitrogen tetroxide
    Dinitrogen tetroxide
    Dinitrogen tetroxide is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium mixture with nitrogen dioxide; some call this mixture dinitrogen tetroxide, while some call it nitrogen dioxide.Dinitrogen tetroxide is a powerful oxidizer, making it highly...

     (N2O4), nitrogen(IV) oxide
  • Dinitrogen pentoxide
    Dinitrogen pentoxide
    Dinitrogen pentoxide is the chemical compound with the formula N2O5. Also known as nitrogen pentoxide, N2O5 is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen...

     (N2O5), nitrogen(V) oxide
  • Trinitramide
    Trinitramide
    Trinitramide is a compound of nitrogen and oxygen with the molecular formula N3. The compound was detected and described in 2010 by researchers at the Royal Institute of Technology in Sweden....

     (N(NO2)3)


In atmospheric chemistry
Atmospheric chemistry
Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary field of research and draws on environmental chemistry, physics, meteorology, computer modeling, oceanography, geology and...

 and air pollution
Air pollution
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....

 and related fields, nitrogen oxides refers specifically to NOx (NO and NO2).

Only the first three of these compounds can be isolated at room temperature. N2O3, N2O4, and N2O5 all decompose rapidly at room temperature. Nitrate radical is very reactive.

N2O is stable and rather unreactive at room temperature, while NO and NO2 are quite reactive but nevertheless quite stable when isolated.

NOx



NOx (often written NOx) refers to NO
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...

 and NO2
Nitrogen dioxide
Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...

. They are produced during combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

, especially at high temperature. These two chemicals are important trace species in Earth's atmosphere. In the troposphere
Troposphere
The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....

, during daylight, NO reacts with partly oxidized organic species (or the peroxy radical
Hydroperoxyl
The hydroperoxyl radical, also known as the perhydroxyl radical, is the protonated form of superoxide with the chemical formula HO2.-Reactivity:The superoxide anion, O2−, and the hydroperoxyl radical are in equilibrium in aqueous solution:...

) to form NO2, which is then photolyzed
Photodissociation
Photodissociation, photolysis, or photodecomposition is a chemical reaction in which a chemical compound is broken down by photons. It is defined as the interaction of one or more photons with one target molecule....

 by sunlight to reform NO:
NO + CH3O2 → NO2 + CH3O
NO2 + sunlight → NO + O


The oxygen atom formed in the second reaction then goes on to form ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...

; this series of reactions is the main source of tropospheric ozone
Tropospheric ozone
Ozone is a constituent of the troposphere . Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night...

. CH3O2 is just one example of many partly oxidized organic molecules that can react with NO to form NO2.

These reactions are rather fast so NO and NO2 cycle, but the sum of their concentration ([NO] + [NO2]) tends to remain fairly constant. Because of this cycling, it is convenient to think of the two chemicals as a group; hence the term NOx.

In addition to acting as a main precursor for tropospheric ozone
Tropospheric ozone
Ozone is a constituent of the troposphere . Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night...

, NOx is also harmful to human health in its own right.

NOx may react with water to make nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

, which may end up in the soil, where it makes nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

, which is of use to growing plants.

Derivatives


Oxidized (cationic) and reduced (anionic) derivatives of many of these oxides exist: nitrite
Nitrite
The nitrite ion has the chemical formula NO2−. The anion is symmetric with equal N-O bond lengths and a O-N-O bond angle of ca. 120°. On protonation the unstable weak acid nitrous acid is produced. Nitrite can be oxidised or reduced, with product somewhat dependent on the oxidizing/reducing agent...

 (NO2-), nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

 (NO3-), nitronium (NO2+), and nitrosonium
Nitrosonium
The nitrosonium ion is NO+, in which the nitrogen atom is bonded to an oxygen atom with a bond order of 3, and the overall diatomic species bears a positive charge. This ion is usually obtained as the following salts: NOClO4, NOSO4H , and NOBF4. The ClO and BF salts are slightly soluble in CH3CN...

(NO+). NO2 is intermediate between nitrite and nitronium:
NO2+ + e → NO2
NO2 + e → NO2