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`acid, from which phosphoruscould bedistilled by heating with charcoal. In the late 1800s
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`James Burgess Readmanof Edinburgh developed an electric furnace method for producing the
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`element from phosphate rock, whichis essentially the method employed today.
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`Occurrence and distribution
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`Phosphorusis a very widely distributed element—12th most abundantin Earth’s crust, to
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`whichit contributes about 0.10 weight percent. Its cosmic abundanceis about one atom per
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`100 atomsofsilicon, the standard. Its high chemical reactivity assures that it does not occur in
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`principal combined formsin nature are the phosphate salts. About 550 different minerals have
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`apatite series in which calcium ions exist along with phosphate ions and variable amounts of
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`fluoride, chloride, or hydroxide ions, according to the formula [Ca,9(PO4)6(F, Cl, or OH)9].
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`Other important phosphorus-bearing minerals are wavellite and vivianite. Commonly, such
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`metal atoms as magnesium, manganese,strontium, and lead substitute for calcium in the
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`mineral, andsilicate, sulfate, vanadate, and similar anions substitute for phosphate ions. Very
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`large sedimentary deposits of fluoroapatite are found in many parts of Earth. The phosphate of
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`bone and tooth enamelis hydroxyapatite. (The principle of lessening tooth decay by
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`fluoridation depends upon the conversion of hydroxyapatite to the harder, more decay-
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`The chief commercial source is phosphorite, or phosphate rock, an impure massive form of
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`carbonate-bearing apatite. Estimates of the total phosphate rock in Earth’s crust average about
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`65,000,000,000 tons, of which Morocco and Western Sahara contain about 80 percent. This
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`estimate includes only ore thatis sufficiently rich in phosphate for conversion to useful
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`products by present methods. Vast quantities of material lower in phosphorus content also
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`exist.
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`The only naturally occurring isotope of phosphorusis that of mass 31. The other isotopes from
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`mass 24 to mass 46 have been synthesized by appropriate nuclear reactions. All of these are
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`radioactive with relatively short half-lives. The isotope of mass 32 hasa half-life of 14.268
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`days and has proven extremely useful in tracer studies involving the absorption and movement
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`Commercial production and uses
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`Deonpecspore acongaton«—sataamar soluble, are valuable additionsto fertilizer. Most of the
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`H3POQ4. About 95 percent of the phosphate rock mined in
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`phosphorususe, however. Most of the phosphorusis
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`up in waterways whereit can cause algal blooms. Another concern is that increased
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`phosphorususage will deplete the nonrenewable supply of phosphate rock.
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`Only about 5 percent of the phosphorus consumedperyear in the United States is used in the
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`elemental form. Pyrotechnic applications of the element includetracers, incendiaries,
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`the rest is employed in chemical synthesis. A large amount is converted to sulfides used in
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`matches and in the manufacture of insecticides and oil additives. Most of the remainderis
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`converted to halides or oxides for subsequent use in synthesizing organic phosphorus
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`The electron configuration of the phosphorus atom can be represented by 1s72572p%3573p3,
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`The outer shell arrangementtherefore resembles that of nitrogen, with three half-filled orbitals
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`each capable of forming a single covalent bond and an additional lone-pair of electrons.
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`Dependingonthe electronegativity of the elements with which it combines, phosphorus can
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`between nitrogen and phosphorusarethat the latter is of considerably lowerelectronegativity
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`and haslarger atoms, with outer d orbitals available. For these reasons, the similarities
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`between nitrogen and phosphorus chemistry are largely formal ones, tending to conceal the
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`actual, wide differences. The outer d orbitals in phosphorus permit an expansion ofthe octet,
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`Thefirst striking difference in chemistry of the two elements is that elemental phosphorus
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`are solid; the three major allotropes are white, red, and black. Phosphorus molecules of
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`formula P», structurally analogous to N» molecules and evidently also triply bonded, exist
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`contrast to the situation with nitrogen, are energetically favoured overonetriple bond. On
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`cooling, the triply bonded Py molecules condense to form tetrahedral P4 molecules, in which
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`alpha form, whichis stable at ordinary temperatures, has a cubic crystal structure; the beta
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`form, whichis stable below —78 °C (—108 °F), has a hexagonal crystal structure. Because of
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`Formation of tetrahedra requires bond angles of 60° instead of the preferred 90°-109° angles,
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`so that white phosphorusisa relatively unstable, or metastable, form. It changes
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`spontaneously, but slowly, at temperatures around 200 °C (390 °F) or higher, to a polymeric
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`form called “red phosphorus.” This substance is amorphous when formed at lower
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`temperatures, but it can becomecrystalline, with a melting point of about 590° C (1,090 °F).
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`At higher temperatures and pressures, or with the aid of a catalyst, at ordinary pressures and a
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`temperature of about 200 °C, phosphorusis converted to a flaky black crystalline form, which
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`despite the relative difficulty in its preparation. In both the red and the black forms, each
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`phosphorus atom forms three single bonds, which are spread apart sufficiently to be relatively
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`covalent bonds, this form is far more reactive chemically than the others.It is highly toxic,
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`reacts vigorously with most reagents, and inflames in air at only 35° C (95 °F), so it must be
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`carbon disulfide, in which it maintains the composition P4. White phosphorushas been used
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`agent. Large quantities are treated with water to make orthophosphoric acid (H3PO,),
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`Phosphorus atoms can bond with oxygen atomsto form ester groups. These can bond with
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`many important biological processes. The phosphoglycerides, for example, are required for
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`living things. Industrially important organic phosphorus compoundsincludeplasticizers and
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`Phosphorusis an important constituent of bones andteeth, and it is essential to the growth of
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`phosphorusis likely to prove very toxic. White phosphorusattacks the skin and, when
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`Phosphorusis presentin the fluids within cells of living tissues as the phosphate ion, PO,",
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`heredity and other cellular functions and are foundin the nucleus of each cell, are molecules of
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`The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Amy Tikkanen.
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`Citation Information
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`Article Title: phosphorus
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`Website Name: Encyclopaedia Britannica
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`Publisher: Encyclopaedia Britannica,Inc.
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`Date Published: 25 February 2024
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`URL:https://www.britannica.comhttps://www.britannica.com/science/phosphorus-chemical-element
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`phosphate
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`phosphate, any of numerous chemical compoundsrelated to phosphoric acid (H3PO4). One
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`group of these derivatives is composed ofsalts containing the phosphate ion (PO,*), the
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`Article Title: phosphate
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`Website Name: Encyclopaedia Britannica
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`Publisher: Encyclopaedia Britannica,Inc.
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`Date Published: 31 January 2024
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