Editing Phosphorus (section)

====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.