Editing Phosphorus (section)

==Compounds==
{{Main category|Phosphorus compounds}}
===Inorganic phosphates===
====Phoshoric acids====
{{main|Phosphoric acids and phosphates}}
The most prevalent compounds of phosphorus are derivatives of phosphate ({{chem2|PO4(3−)}}), a tetrahedral anion.{{r|Corbridge1995}} Phosphate is the conjugate base of phosphoric acid, which is produced on a massive scale for use in fertilisers. Being triprotic, phosphoric acid converts stepwise to three conjugate bases:
:{{chem2|H3PO4 + H2O <-> H3O+ + H2PO4-}} (''K''<sub>a1</sub>&thinsp;= 7.25×10<sup>−3</sup>)
:{{chem2|H2PO4- + H2O <-> H3O+ + HPO4(2-)}} (''K''<sub>a2</sub>&nbsp;= 6.31×10<sup>−8</sup>)
:{{chem2|HPO4(2-) + H2O <-> H3O+ + PO4(3-)}} (''K''<sub>a3</sub>&nbsp;= 3.98×10<sup>−13</sup>)

Food-grade [[phosphoric acid]] (additive [[E number|E338]]{{r|FGOVUK}}) is used to acidify foods and beverages such as various [[cola]]s and jams, providing a tangy or sour taste.{{r|Threlfall1951}} The phosphoric acid also serves as a [[preservative]].{{r|Coca-ColaGB}} Soft drinks containing phosphoric acid, including [[Coca-Cola]], are sometimes called [[phosphate soda]]s or phosphates. Phosphoric acid in soft drinks has the potential to cause dental erosion,{{r|Moynihan2002}} as well as contribute to the formation of [[Kidney stone disease|kidney stones]], especially in those who have had kidney stones previously.{{r|Qaseem2014}}

====Metal salts====
With metal [[cation]]s, phosphate forms a variety of salts. These solids are polymeric, featuring P-O-M linkages. When the metal cation has a charge of 2+ or 3+, the salts are generally insoluble, hence they exist as common minerals. Many phosphate salts are derived from hydrogen phosphate ({{chem2|HPO4(2-)}}).

Calcium phosphates in particular are widespread compounds with many applications. Among them, they are used to improve the characteristics of processed meat and [[cheese]], in [[baking powder]], and in toothpaste.{{r|Threlfall1951}} Two of the most relevant among them are [[monocalcium phosphate]], and [[dicalcium phosphate]].

====Polyphosphates====
Phosphate exhibits a tendency to form chains and rings containing P-O-P bonds. Many polyphosphates are known, including [[Adenosine triphosphate|ATP]]. Polyphosphates arise by dehydration of hydrogen phosphates such as {{chem2|HPO4(2-)}} and {{chem2|H2PO4-}}. For example, the industrially important pentasodium triphosphate (also known as [[sodium tripolyphosphate]], STPP) is produced industrially by the megatonne by this [[condensation reaction]]:
:{{chem2|2 Na2HPO4 + NaH2PO4 -> Na5P3O10 + 2 H2O}}
Sodium triphosphate is used in laundry detergents in some countries, but banned for this use in others.{{r|Hammond2000}} This compound [[water softening|softens]] the water to enhance the performance of the detergents and to prevent pipe and boiler tube [[corrosion]].{{r|Schrödter2008}}

====Oxoacids====
{{main|Phosphorus oxoacids}}
Phosphorus [[oxoacid]]s are extensive, often commercially important, and sometimes structurally complicated. They all have acidic protons bound to oxygen atoms, some have nonacidic protons that are bonded directly to phosphorus and some contain phosphorus–phosphorus bonds.{{r|Greenwood1997}} Although many oxoacids of phosphorus are formed, only nine are commercially important. Among them, hypophosphorous, phosphorous and orthophosphoric acid are particularly important.

{|class="wikitable"
|-
!Oxidation state!!Formula!!Name!!Acidic protons!!Compounds
|-
| +1||{{chem2|HH2PO2}}||[[hypophosphorous acid]]||1||acid, salts
|-
| +3||{{chem2|H3PO3}}||[[phosphorous acid]]<br />(phosphonic acid)||2||acid, salts
|-
| +3||{{chem2|HPO2}}||metaphosphorous acid||1||salts
|-
| +4||{{chem2|H4P2O6}}||[[hypophosphoric acid]]||4||acid, salts
|-
| +5||{{chem2|(HPO3)_{''n''}|}}||[[metaphosphoric acid]]s||''n''||salts (''n''&nbsp;=&nbsp;3,4,6)
|-
| +5||{{chem2|H(HPO3)_{''n''}OH}}||[[polyphosphoric acid]]s||''n''+2||acids, salts (''n''&nbsp;=&thinsp;1-6)
|-
| +5||{{chem2|H5P3O10}}||[[tripolyphosphoric acid]]||3||salts
|-
| +5||{{chem2|H4P2O7}}||[[pyrophosphoric acid]]||4||acid, salts
|-
| +5||{{chem2|H3PO4}}||(ortho)[[phosphoric acid]]||3||acid, salts
|}

===Other inorganic compounds===
====Oxides and sulfides====
{{main|phosphorus oxides|phosphorus sulfides}}
[[File:Phosphorus-pentoxide-3D-balls.png|thumb|right|The tetrahedral structure of {{chem2|P4O10}} and {{chem2|P4S10}}]]
[[Phosphorus pentoxide]] ({{chem2|P4O10}}) is the [[acid anhydride]] of phosphoric acid, but several intermediates between the two are known. This waxy white solid reacts vigorously with water. Similarly, [[phosphorus trioxide]] ({{chem2|P4O6}}, also called tetraphosphorus hexoxide) is the anhydride of {{chem2|P(OH)3}}, the minor tautomer of phosphorous acid. The structure of {{chem2|P4O6}} is like that of {{chem2|P4O10}} without the terminal oxide groups. Mixed oxyhalides and oxyhydrides of phosphorus(III) are almost unknown. Meanwhile, phosphorus forms a wide range of sulfides, where the phosphorus can be in P(V), P(III) or other oxidation states. However, only two of them are commercially significant. [[Phosphorus pentasulfide]] ({{chem2|P4S10}}) has a structure analogous to {{chem2|P4O10}}, and is used in the manufacture of additives and pesticides.{{r|Heal1980}} The three-fold symmetric [[Phosphorus sesquisulfide]] ({{chem2|P4S3}}) is used in [[strike-anywhere match]]es.

====Halides====
{{main|phosphorus halides}}
Phosphorus [[halide]]s can have as oxidation state +3 in the case of trihalides and +5 for pentahalides and [[Chalcogen#With halogens|chalcoalide]]s, but also +2 for disphosphorus tetrahalides. All four symmetrical trihalides are well known: gaseous {{chem2|PF3|link=phosphorus trifluoride}}, the yellowish liquids {{chem2|PCl3|link=phosphorus trichloride}} and {{chem2|PBr3|link=phosphorus tribromide}}, and the solid {{chem2|PI3|link=phosphorus triiodide}}. These materials are moisture sensitive, hydrolysing to give [[phosphorous acid]]. The trichloride, a common reagent used for the manufacture of pesticides, is produced by chlorination of white phosphorus. The trifluoride is produced from the trichloride by halide exchange. {{chem2|PF3}} is toxic because it binds to [[haemoglobin]].

Most phosphorus pentahalides are common compounds. {{chem2|PF5|link=phosphorus pentafluoride}} is a colourless gas and the molecules have a [[trigonal bipyramid]]al geometry. With fluoride, it forms {{chem2|PF6-}}, an [[anion]] that is [[isoelectronic]] with {{chem2|SF6|link=sulfur hexafluoride}}. {{chem2|PCl5|link=phosphorus pentachloride}} is a colourless solid which has an ionic formulation of {{chem2|PCl4+PCl6-}}, but adopts a trigonal bipyramidal geometry when molten or in the vapour phase.{{r|Greenwood1997}} Both the pentafluoride and the pentachloride are [[Lewis acid]]s. Meanwhile, {{chem2|PBr5|link=phosphorus pentabromide}} is an unstable solid formulated as {{chem2|PBr4+Br-}}. {{chem2|PI5|link=phosphorus pentaiodide}} is not known.{{r|Greenwood1997}}

The most important phosphorus [[oxyhalide]] is [[phosphorus oxychloride]] ({{chem2|POCl3}}), which is approximately tetrahedral. It is prepared from {{chem2|PCl3}} and used in the manufacture of plasticizers. Phosphorus can also form thiohalides such as {{chem2|PSCl3|link=Thiophosphoryl chloride}}, and in rare cases selenohalides.

====Nitrides====
The PN molecule [[phosphorus mononitride]] is considered unstable, but is a product of crystalline [[triphosphorus pentanitride]] decomposition at {{convert|1100|K|C}}. Similarly, {{chem2|H2PN}} is considered unstable, and phosphorus nitride halogens like {{chem2|F2PN}}, {{chem2|Cl2PN}}, {{chem2|Br2PN}}, and {{chem2|I2PN}} oligomerise into cyclic [[polyphosphazene]]s. For example, compounds of the formula {{chem2|(PNCl2)_{''n''}|}} exist mainly as rings such as the [[trimer (chemistry)|trimer]] [[hexachlorophosphazene]]. The phosphazenes arise by treatment of phosphorus pentachloride with ammonium chloride:
:{{chem2|PCl5 + NH4Cl -> 1/''n'' (NPCl2)_{''n''} + 4 HCl}}
When the chloride groups are replaced by [[alkoxide]] ({{chem2|RO-}}), a family of polymers is produced with potentially useful properties.{{r|Mark1992}}

====Phosphides and phosphine====
{{main|Phosphide|Template:Phosphides}}
A wide variety of compounds which contain the containing the phosphide ion {{chem2|P(3−)}} exist, both with [[main-group element]]s and with [[metal]]s. They often exhibit complex structures, where phosphorus has the −3 oxidation state. Metal phosphides arise by reaction of metals with red phosphorus. The [[alkali metal]]s (group 1) and [[alkaline earth metal]]s (group 2) can also form compounds such as {{chem2|Na3P7|link=sodium phosphide}}. These compounds react with water to form [[phosphine]].{{r|Greenwood1997}} Some phosphide minerals are also known, like {{chem2|(Fe,Ni)2P|link=Allabogdanite}} and {{chem2|(Fe,Ni)3P|link=Schreibersite}}, but they are very rare on Earth, most instances occurring in [[Iron meteorite|iron-nickel meteorite]]s.

Phosphine ({{chem2|PH3}}) and its organic derivatives are structural analogues of [[ammonia]] ({{chem2|NH3}}), but the bond angles at phosphorus are closer to 90° for phosphine and its organic derivatives. It is an ill-smelling and toxic gas, produced by hydrolysis of [[calcium phosphide]] ({{chem2|Ca3P2}}). Unlike ammonia, phosphine is oxidised by air. Phosphine is also far less basic than ammonia. Other phosphines are known which contain chains of up to nine phosphorus atoms and have the formula {{chem2|P_{''n''}H_{''n''+2}|}}.{{r|Greenwood1997}} The highly flammable gas [[diphosphine]] ({{chem2|P2H4}}) is an analogue of [[hydrazine]].

===Organophosphorus compounds===
{{Main|organophosphorus chemistry}}
[[File:YoshifujiR2P2.png|thumb|right|A stable diphosphene, a derivative of phosphorus(I)]]
====Phosphines, phosphites and organophosphates====
{{main|phosphaalkenes|organophosphates}}
Compounds with P-C and P-O-C bonds are often classified as organophosphorus compounds. They are widely used commercially. The {{chem2|P(3+)}} serves as a source of {{chem2|PCl3}} in routes to organophosphorus(III) compounds. For example, it is the precursor to [[triphenylphosphine]]:
:{{chem2|PCl3 + 6 Na + 3 C6H5Cl -> P(C6H5)3 + 6 NaCl}}
Treatment of phosphorus trihalides with alcohols and [[phenol]]s gives phosphites, e.g. [[triphenylphosphite]]:
:{{chem2|PCl3 + 3 C6H5OH -> P(OC6H5)3 + 3 HCl}}
Similar reactions occur for [[phosphorus oxychloride]], affording [[triphenylphosphate]]:
:{{chem2|OPCl3 + 3 C6H5OH -> OP(OC6H5)3 + 3 HCl}}

Some organophosphates are used as flame retardants.{{r|Naiker2023}} Among them, [[tricresyl phosphate]] and [[2-Ethylhexyl diphenyl phosphate|2-ethylhexyl diphenyl phosphate]] are also [[plasticisers]], making these two properties useful in the production of non-flammable plastic products and derivatives.{{r|Greenwood1997|Diskowski2000}}

While many organic compounds of phosphorus are required for life, some are highly toxic. A wide range of organophosphorus compounds are used for their toxicity as [[pesticide]]s and [[weapon]]ised as [[nerve agent]]s.{{r|Greenwood1997}} Some notable examples include [[sarin]], [[VX (nerve agent)|VX]] or [[Tabun (nerve agent)|Tabun]]. Fluorophosphate [[ester]]s (like sarin) are among the most potent [[neurotoxin]]s known.

====Thioesters====
Symmetric phosphorus(III) trithioesters (e.g. {{chem2|P(SMe)3}}) can be produced from the reaction of [[white phosphorus]] and the corresponding [[disulfide]], or phosphorus(III) halides and [[thiolate]]s. Unlike the corresponding esters, they do not undergo a variant of the [[Michaelis-Arbuzov reaction]] with electrophiles.  Instead, they revert to another phosphorus(III) compound through a [[sulfonium]] intermediate.{{r|Senning1971}}

====Phosphorus(I) and phosphorus(II)====
{{main|diphosphenes|diphosphane#organic diphosphanes}}
These compounds generally feature P–P bonds.{{r|Greenwood1997}} Examples include catenated derivatives of phosphine and organophosphines. Compounds containing P=P double bonds have also been observed, although they are rare.