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About Phosphorus

Phosphorus Bohr

Like its close chemical relative, nitrogen, phosphorus is a nonmetallic element with a seemingly contradictory nature. Found in fundamental organic compounds such as DNA, ATP, and phospholipids, phosphorus is essential to life, yet it is also a component of dangerous explosives and some of the most potent poisons known, organophosphate nerve agents. However, upon closer consideration, these two sides of phosphorus are in fact inextricably connected: phosphorus would be incapable of playing its myriad biochemical roles without the very chemical properties that make it so reactive in isolation, while the lethal effects of nerve agents requires their structural similarity to the natural target of an enzyme which they irreversibly inhibit. The complex chemistry of phosphorus lends it to these roles and many others, making it an element that defies simple characterizations.

Despite its ubiquity, phosphorus was not known as an element for most of human history, as it is too reactive to be found naturally outside of compounds. Elemental phosphorus was first isolated by Hennig Brand in 1669. Brand was an alchemist who was experimenting with urine in an attempt to produce the philosopher’s stone, and instead produced a mysterious waxy white substance that glowed in the dark--a phenomenon now known to result from a slow light-producing reaction with oxygen. Brand showed his discovery to a number of others, and eventually sold his methods to D Krafft, who proceeded to exhibit the substance around Europe. The secret that the substance was produced from urine was soon leaked, leading to the production of the element by many other chemists.

Matches were the first commercial use for phosphorus, but the early match industry was fraught with problems. White phosphorus, the form isolated by Brand, was both extremely unstable and toxic, and early matches caused accidental fires and poisonings of the workers who produced them. However, in 1850, Anton Schrotter von Kristelli showed that through controlled heating, white phosphorus could be transformed into a red substance that was more stable and that did not produce toxic phosphorus fumes. Today it is known that elemental phosphorus can additionally be induced to form even more stable violet and black crystalline forms through the application of temperature or pressure, though the red and white forms remain the most used. The use of red phosphorus, as well as various safety-enhancing design elements, such as the separation of reactive elements on match heads and a special striking surface in “safety matches”, allowed for the widespread use and production of considerably safer phosphorus matches.

In 1769, Johan Gottlieb Gahn and Carl Wilhelm Scheele showed that bones contained calcium phosphate, and that the pure element could be extracted from bone ash. Bone remained the major source of the element for the next seventy years. In the 1840s, it was recognized that bat and bird guano was another important source of phosphates, particularly for use in fertilizer. As early as 1850, phosphate rock was also used for a phosphorus source, but this method of production was very significant until after the development of electric arc furnace in 1890, which made the process significantly more feasible.

Industrial extraction of phosphorus from phosphate rock did not begin to approach the scale of today’s phosphorus industry until the World Wars, during which white phosphorus was used widely in weapons. Phosphorus is used in many incendiary devices, such as incendiary bombs and molotov cocktails, as well as in smoke screens. Phosphorus burns vigorously, producing fires that are difficult to extinguish and horrific wounds when it contacts human skin. Interestingly, its use is still allowed for bombs and smoke-producing munitions, but it is classified as a chemical agent when used in direct bombardment, and therefore this use is prohibited. The organophosphates developed for warfare are also considered illegal chemical weapons, though many countries still retain stockpiles of these compounds, which include VX and sarin gas. However, organophosphate pesticides, which operate through the exact same mechanism as these chemical weapons--the inhibition of acetylcholinesterase, which is necessary for normal nerve function-- and can be lethal in small doses when inhaled, ingested, or even absorbed through the skin, remain common tools in commercial agriculture. The potency of these compounds, as well as their extremely quick action in the body and their wide availability make them one of the most common causes of poisonings worldwide, and they are often implicated in suicides in rural areas.

The use of phosphates in fertilizer, while less immediately toxic, is another aspect of modern agriculture with sometimes troubling side-effects. Phosphorus is often a limiting nutrient in marine ecosystems, and phosphate-rich runoff from over-fertilized fields is therefore often the cause of overgrowth, which manifests as algal blooms. At minimum, a sudden growth of algae, followed by its die-off and decay, consumes dissolved oxygen in the water, producing hypoxic conditions that kill off animals and plants in large numbers. In particularly concerning cases, the species of algae in the bloom are themselves dangerous, producing neurotoxins that kill marine life directly and also accumulate in seafood, leading to poisonings. Despite these problems, fertilizer remains the largest use of industrially produced phosphorus. The use of phosphates as chelating water softening agents, often to increase the effectiveness of detergents, is also known to contribute to harmful effects of phosphate on the environment.

Beyond fertilizers, poisons, and water-softening agents, there are a number of other phosphate compounds with important applications. Various inorganic phosphates are used as food additives, often as leavening agents. Trisodium phosphate is widely used in cleaning agents and disinfectants, and sometimes as a flux in ceramic glazes or solder. Zinc dithiophoshate is a common anti-wear additive used in automotive lubricants such as motor oil. Tricresyl and tributyl phosphates are important plasticizers, used to produce nitrocellulose, acyrlates, and PVC, and also serve as solvents in inks, resins, and adhesives. Glyophosphate, known commercially as Roundup, is an widely-used systemic herbicides. Other important organophosphorus compounds include organic derivatives of phosphine, the phosphorus analogue of ammonia, which itself is used to produce many specialty phosphate chemicals and as pesticides and fumigants.

Phosphorus has a number of other commercial uses. In addition to being used to produce fertilizers and various industrial phosphates, phosphoric acid may be used for rust removal as an etching agent in dentistry, or for the production of phosphoric acid fuel cells. Phosphazenes are nitrogen-phosphorus compounds used to produce hybrid organic-inorganic polymers that can be engineered to have highly desirable properties. These polymers have been used to produce drug-delivering gels that degrade in the body, polymer electrolytes with potential for use in fuel cells and batteries, and elastomers that can withstand a variety of chemical and thermal environments, which frequently find use in aerospace components. Pure phosphorus is also used directly in metallurgy to make phosphor bronze, and sometimes finds use as a dopant to manipulate the electrical properties of semiconductors.

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Elemental Forms

Phosphorus Properties

Phosphorus (P) atomic and molecular weight, atomic number and elemental symbolPhosphorus Bohr ModelPhosphorus (atomic symbol: P, atomic number: 15) is a Block P, Group 15, Period 3 element. The number of electrons in each of Phosphorus's shells is 2, 8, 5 and its electronic configuration is [Ne] 3s2 3p3. The phosphorus atom has a radius of and its Van der Waals radius is Black PhosphorusPhosphorus is a highly-reactive non-metallic element (sometimes considered a metalloid) with two primary allotropes, white phosphorus and red phosphorus. Compound forms of phosphorus include phosphates and phosphides. Phosphorous was first recognized as an element by Hennig Brand in 1669; its name (phosphorus mirabilis, or "bearer of light") was inspired from the brilliant glow emitted by its distillation.

Symbol: P
Atomic Number: 15
Atomic Weight: 30.97
Element Category: nonmetal
Group, Period, Block: 15 (pnictogens), 3, p
Color: colourless/red/silvery white/ pale yellow
Other Names: Phosphore, Phosphor, Fosforo
Melting Point: 44.15 °C, 111.47 °F, 317.3 K
Boiling Point: 280.5 °C, 536.9 °F, 553.65 K
Density: 1820 kg·m3
Liquid Density @ Melting Point: N/A
Density @ 20°C: 1.82 g/cm3
Density of Solid: 1823 kg·m3
Specific Heat: N/A
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 2.51
Heat of Vaporization (kJ·mol-1): 51.9
Heat of Atomization (kJ·mol-1): 314
Thermal Conductivity: (white) 0.236, (black) 12.1 W·m-1·K-1
Thermal Expansion: N/A
Electrical Resistivity: N/A
Tensile Strength: N/A
Molar Heat Capacity: 23.824 J·mol-1·K-1
Young's Modulus: N/A
Shear Modulus: N/A
Bulk Modulus: (white) 5, (red) 11 GPa
Poisson Ratio: N/A
Mohs Hardness: N/A
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: N/A
Pauling Electronegativity: 2.19
Sanderson Electronegativity: 2.52
Allred Rochow Electronegativity: 2.06
Mulliken-Jaffe Electronegativity: 2.30 (20% s orbital)
Allen Electronegativity: 2.253
Pauling Electropositivity: 1.81
Reflectivity (%): N/A
Refractive Index: 1.001212 
Electrons: 15
Protons: 15
Neutrons: 16
Electron Configuration: [Ne] 3s2 3p3
Atomic Radius: N/A
Atomic Radius,
non-bonded (Å):
Covalent Radius: 107±3 pm
Covalent Radius (Å): 1.09
Van der Waals Radius: 180 pm
Oxidation States: 5, 3, -3
Phase: Solid
Crystal Structure: triclinic
Magnetic Ordering: diamagnetic
Electron Affinity (kJ·mol-1) 72.075
1st Ionization Energy: 1011.82 kJ·mol-11
2nd Ionization Energy: 1907.47 kJ·mol-1
3rd Ionization Energy: 2914.14 kJ·mol-1
CAS Number: 7723-14-0
EC Number: N/A
MDL Number: MFCD00133771
Beilstein Number: N/A
SMILES Identifier: P
InChI Identifier: InChI=1S/P
PubChem CID: 24404
ChemSpider ID: 4575369
Earth - Total: 1920 ppm 
Mercury - Total: 390 ppm
Venus - Total: 1860 ppm
Earth - Seawater (Oceans), ppb by weight: 70
Earth - Seawater (Oceans), ppb by atoms: 14
Earth -  Crust (Crustal Rocks), ppb by weight: 1000000
Earth -  Crust (Crustal Rocks), ppb by atoms: 700000
Sun - Total, ppb by weight: 7000
Sun - Total, ppb by atoms: 300
Stream, ppb by weight: 20
Stream, ppb by atoms: 0.6
Meterorite (Carbonaceous), ppb by weight: 1100000
Meterorite (Carbonaceous), ppb by atoms: 700000
Typical Human Body, ppb by weight: 11000000
Typical Human Body, ppb by atom: 2200000
Universe, ppb by weight: 7000
Universe, ppb by atom: 300
Discovered By: Hennig Brand
Discovery Date: 1669
First Isolation: N/A

Health, Safety & Transportation Information for Phosphorus

Although white phosphorus is very toxic, red phosphorus is not considered toxic. Safety data for phosphorus and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific material or compound referenced in the Products tab. The below information applies to elemental Phosphorus.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Danger
Hazard Statements H228-H412
Hazard Codes F
Risk Codes 11-16-52/53
Safety Precautions 7-43-61
RTECS Number TH3495000
Transport Information UN 1338 4.1/PG 3
WGK Germany 2
Globally Harmonized System of
Classification and Labelling (GHS)

Phosphorus Isotopes

Phosphorus has one stable isotope: 31P.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
24P 24.03435(54)# N/A p to 23Si; ß+ to 24Si (1+)# N/A 145.38 -
25P 25.02026(21)# <30 ns p to 24Si (1/2+)# N/A 166.5 -
26P 26.01178(21)# 43.7(6) ms ß+ to 26Si; ß+ + 2p to 26Mg; ß+ + p to 25Al (3+) N/A 182.97 -
27P 26.999230(28) 260(80) ms ß+ to 27Si; ß+ + p to 26Al 1/2+ N/A 202.23 -
28P 27.992315(4) 270.3(5) ms ß+ to 28Si; ß+ + p to 27Al; ß+ + a to 24Si 3+ N/A 216.83 -
29P 28.9818006(6) 4.142(15) s EC to 29Si 1/2+ 1.2349 235.15 -
30P 29.9783138(3) 2.498(4) min EC to 30Si 1+ N/A 246.03 -
31P 30.97376163(20) STABLE - 1/2+ 1.1316 258.76 100
32P 31.97390727(20) 14.263(3) d ß- to 32S 1+ -0.2524 266.84 -
33P 32.9717255(12) 25.34(12) d ß- to 33S 1/2+ N/A 276.78 -
34P 33.973636(5) 12.43(8) s ß- to 34S 1+ N/A 283 -
35P 34.9733141(20) 47.3(7) s ß- to 35S 1/2+ N/A 291.08 -
36P 35.978260(14) 5.6(3) s ß- to 36S 4-# N/A 294.5 -
37P 36.97961(4) 2.31(13) s ß- to 37S 1/2+# N/A 301.65 -
38P 37.98416(11) 0.64(14) s ß- + n to 38S; ß- + n to 37S N/A N/A 305.07 -
39P 38.98618(11) 190(50) ms ß- + n to 39S; ß- + n to 38S 1/2+# N/A 311.28 -
40P 39.99130(15) 153(8) ms ß- + n to 40S; ß- + n to 39S (2-,3-) N/A 314.7 -
41P 40.99434(23) 100(5) ms ß- + n to 41S; ß- + n to 40S 1/2+# N/A 319.99 -
42P 42.00101(48) 48.5(15) ms ß- + n to 42S; ß- + n to 41S N/A N/A 321.54 -
43P 43.00619(104) 36.5(15) ms ß- + n to 43S 1/2+# N/A 324.96 -
44P 44.01299(75)# 18.5(25) ms ß- to 44S N/A N/A 327.45 -
45P 45.01922(86)# 8# ms [>200 ns] ß- to 45S 1/2+# N/A 329.01 -
46P 46.02738(97)# 4# ms [>200 ns] ß- to 46S N/A N/A 329.64 -