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Phosphorous

Phosphorous

Gist

Phosphorus is a chemical element with the symbol P and atomic number 15. It is a nonmetal, essential for life, and found in various forms, including white, red, and black phosphorus. It plays a vital role in bone and teeth formation, energy production (ATP), and cell membrane structure. Most of the phosphorus in the body is found in bones and teeth.

It is a nonmetal, a pnictogen, and a period 3 element. It is essential for all living organisms and plays a crucial role in bone and teeth formation, energy production (ATP), and various other biochemical processes.

Summary

Phosphorus is a chemical element; it has symbol P and atomic number 15. All elemental forms of phosphorus are highly reactive and are therefore never found in nature. They can nevertheless be prepared artificially, the two most common allotropes being white phosphorus and red phosphorus. With 31P as its only stable isotope, phosphorus has an occurrence in Earth's crust of about 0.1%, generally as phosphate rock. A member of the pnictogen family, phosphorus readily forms a wide variety of organic and inorganic compounds, with as its main oxidation states +5, +3 and −3.

The isolation of white phosphorus in 1669 by Hennig Brand marked the scientific community's first discovery of an element since Antiquity. The name phosphorus is a reference to the god of the Morning star in Greek mythology, inspired by the faint glow of white phosphorus when exposed to oxygen. This property is also at the origin of the term phosphorescence, meaning glow after illumination, although white phosphorus itself does not exhibit phosphorescence, but chemiluminescence caused by its oxidation. Its high toxicity makes exposure to white phosphorus very dangerous, while its flammability and pyrophoricity can be weaponised in the form of incendiaries. Red phosphorus is less dangerous and is used in matches and fire retardants.

Most industrial production of phosphorus is focused on the mining and transformation of phosphate rock into phosphoric acid for phosphate-based fertilisers. Phosphorus is an essential and often limiting nutrient for plants, and while natural levels are normally maintained over time by the phosphorus cycle, it is too slow for the regeneration of soil that undergoes intensive cultivation. As a consequence, these fertilisers are vital to modern agriculture. The leading producers of phosphate ore in 2024 were China, Morocco, the United States and Russia, with two-thirds of the estimated exploitable phosphate reserves worldwide in Morocco alone. Other applications of phosphorus compounds include pesticides, food additives, and detergents.

Phosphorus is essential to all known forms of life, largely through organophosphates, organic compounds containing the phosphate ion as a functional group. These include DNA, RNA, ATP, and phospholipids, complex compounds fundamental to the functioning of all cells. The main component of bones and teeth, bone mineral, is a modified form of hydroxyapatite, itself a phosphorus mineral.

Details

Phosphorus (P) is a nonmetallic chemical element of the nitrogen family (Group 15 [Va] of the periodic table) that at room temperature is a colourless, semitransparent, soft, waxy solid that glows in the dark.

Element Properties

atomic number  :  15
atomic weight  :  30.9738
melting point (white)  :  44.1 °C (111.4 °F)
boiling point (white)  :  280 °C (536 °F)
density (white)  :  1.82 gram/{cm}^{3} at 20 °C (68 °F)
oxidation states  :  −3, +3, +5.

History

Arabian alchemists of the 12th century may have isolated elemental phosphorus by accident, but the records are unclear. Phosphorus appears to have been discovered in 1669 by Hennig Brand, a German merchant whose hobby was alchemy. Brand allowed 50 buckets of urine to stand until they putrified and “bred worms.” He then boiled the urine down to a paste and heated it with sand, thereby distilling elemental phosphorus from the mixture. Brand reported his discovery in a letter to Gottfried Wilhelm Leibniz, and, thereafter, demonstrations of this element and its ability to glow in the dark, or “phosphoresce,” excited public interest. Phosphorus, however, remained a chemical curiosity until about a century later when it proved to be a component of bones. Digestion of bones with nitric or sulfuric acid formed phosphoric acid, from which phosphorus could be distilled by heating with charcoal. In the late 1800s James Burgess Readman of Edinburgh developed an electric furnace method for producing the element from phosphate rock, which is essentially the method employed today.

Occurrence and distribution

Phosphorus is a very widely distributed element—12th most abundant in crust Earth’s , to which it contributes about 0.10 weight percent. Its cosmic abundance is about one atom per 100 atoms of silicon, the standard. Its high chemical reactivity assures that it does not occur in the free state (except in a few meteorites). Phosphorus always occurs as the phosphate ion. The principal combined forms in nature are the phosphate salts. About 550 different minerals have been found to contain phosphorus, but, of these, the principal source of phosphorus is the apatite series in which calcium ions exist along with phosphate ions and variable amounts of fluoride, chloride, or hydroxide ions, according to the formula [Ca10(PO4)6(F, Cl, or OH)2]. Other important phosphorus-bearing minerals are wavellite and vivianite. Commonly, such metal atoms as magnesium, manganese, strontium, and lead substitute for calcium in the mineral, and silicate, sulfate, vanadate, and similar anions substitute for phosphate ions. Very large sedimentary deposits of fluoroapatite are found in many parts of Earth. The phosphate of bone and tooth enamel is hydroxyapatite. (The principle of lessening tooth decay by fluoridation depends upon the conversion of hydroxyapatite to the harder, more decay-resistant, fluoroapatite.)

The chief commercial source is phosphorite, or phosphate rock, an impure massive form of carbonate-bearing apatite. Estimates of the total phosphate rock in Earth’s crust average about 65,000,000,000 tons, of which Morocco and Western Sahara contain about 80 percent. This estimate includes only ore that is sufficiently rich in phosphate for conversion to useful products by present methods. Vast quantities of material lower in phosphorus content also exist.

The only naturally occurring isotope of phosphorus is that of mass 31. The other isotopes from mass 24 to mass 46 have been synthesized by appropriate nuclear reactions. All of these are radioactive with relatively short half-lives. The isotope of mass 32 has a half-life of 14.268 days and has proven extremely useful in tracer studies involving the absorption and movement of phosphorus in living organisms.

Commercial production and uses

The principal technique for converting phosphate rock to usable materials involves acidulation of the crushed rock—with either sulfuric or phosphoric acids—to form crude calcium hydrogen phosphates that, being water-soluble, are valuable additions to fertilizer. Most of the output is burned to phosphoric anhydride and subsequently treated with water to form phosphoric acid, H3PO4. About 95 percent of the phosphate rock mined in the United States is used to make fertilizer or food supplements for animals. Concerns have arisen about phosphorus use, however. Most of the phosphorus is wasted on its journey from mining to being eaten by humans, and the wasted phosphorus ends up in waterways where it can cause algal blooms. Another concern is that increased phosphorus usage will deplete the nonrenewable supply of phosphate rock.

Only about 5 percent of the phosphorus consumed per year in the United States is used in the elemental form. Pyrotechnic applications of the element include tracers, incendiaries, fireworks, and matches. Some is used as an alloying agent, some is used to kill rodents, and the rest is employed in chemical synthesis. A large amount is converted to sulfides used in matches and in the manufacture of insecticides and oil additives. Most of the remainder is converted to halides or oxides for subsequent use in synthesizing organic phosphorus compounds.

Additional Information:

Appearance

The two main forms of phosphorus are white phosphorus and red phosphorus. White phosphorus is a poisonous waxy solid and contact with skin can cause severe burns. It glows in the dark and is spontaneously flammable when exposed to air. Red phosphorus is an amorphous non-toxic solid.

Uses

White phosphorus is used in flares and incendiary devices. Red phosphorus is in the material stuck on the side of matchboxes, used to strike safety matches against to light them.

By far the largest use of phosphorus compounds is for fertilisers. Ammonium phosphate is made from phosphate ores. The ores are first converted into phosphoric acids before being made into ammonium phosphate.

Phosphorus is also important in the production of steel. Phosphates are ingredients in some detergents, but are beginning to be phased out in some countries. This is because they can lead to high phosphate levels in natural water supplies causing unwanted algae to grow. Phosphates are also used in the production of special glasses and fine chinaware.

Biological role

Phosphorus is essential to all living things. It forms the sugar-phosphate backbone of DNA and RNA. It is important for energy transfer in cells as part of ATP (adenosine triphosphate), and is found in many other biologically important molecules. We take in about 1 gram of phosphate a day, and store about 750 grams in our bodies, since our bones and teeth are mainly calcium phosphate. Over-use of phosphates from fertilisers and detergents can cause them to pollute rivers and lakes causing algae to grow rapidly. The algae block out light stopping further photosynthesis. Oxygen dissolved in the water soon gets used up and the lake dies.

Natural abundance

Phosphorus is not found uncombined in nature, but is widely found in compounds in minerals. An important source is phosphate rock, which contains the apatite minerals and is found in large quantities in the USA and elsewhere. There are fears that ‘peak phosphorus’ will occur around 2050, after which our sources will dwindle.

White phosphorus is manufactured industrially by heating phosphate rock in the presence of carbon and silica in a furnace. This produces phosphorus as a vapour, which is then collected under water. Red phosphorus is made by gently heating white phosphorus to about 250°C in the absence of air.

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