Editing Period 3 element (section)

=== Phosphorus ===
{{Main|Phosphorus}}
''Phosphorus'' (symbol '''P''') is a [[Valency (chemistry)|multivalent]] [[Nonmetal (chemistry)|nonmetal]] of the [[pnictogen|nitrogen group]], phosphorus as a mineral is almost always present in its maximally oxidized ([[pentavalent]]) state, as inorganic [[phosphate minerals|phosphate rocks]]. Elemental phosphorus exists in two major forms—[[white phosphorus]] and [[red phosphorus]]—but due to its high reactivity, phosphorus is never found as a free element on Earth.

The first form of elemental phosphorus to be produced (white phosphorus, in 1669) emits a faint glow upon exposure to [[oxygen]] – hence its name given from Greek mythology, {{lang|el|Φωσφόρος}} meaning "light-bearer" (Latin: ''[[Lucifer]]''), referring to the "[[Hesperus|Morning Star]]", the planet [[Venus]]. Although the term "[[phosphorescence]]", meaning glow after illumination, derives from this property of phosphorus, the glow of phosphorus originates from oxidation of the white (but not red) phosphorus and should be called [[chemiluminescence]]. It is also the lightest element to easily produce stable exceptions to the [[octet rule]].

The vast majority of phosphorus compounds are consumed as fertilizers. Other applications include the role of [[organophosphorus compound]]s in [[detergent]]s, [[pesticide]]s and [[nerve agents]] and [[match]]es.<ref>Herbert Diskowski, Thomas Hofmann "Phosphorus" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a19_505}}</ref>