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Black phosphorus is the thermodynamically stable form of phosphorus at room temperature and pressure, with a heat of formation of −39.3 kJ/mol (relative to white phosphorus which is defined as the standard state). [1] It was first synthesized by heating white phosphorus under high pressures (12,000 atmospheres) in 1914.
White phosphorus is the least stable, the most reactive, the most volatile, the least dense and the most toxic of the allotropes. White phosphorus gradually changes to red phosphorus, accelerated by light and heat. Samples of white phosphorus almost always contain some red phosphorus and accordingly appear yellow.
Although phosphorus (15 P) has 22 isotopes from 26 P to 47 P, only 31 P is stable; as such, phosphorus is considered a monoisotopic element. The longest-lived radioactive isotopes are 33 P with a half-life of 25.34 days and 32 P with a half-life of 14.268 days. [3] [4] All others have half-lives of under 2.5 minutes, most under a second.
Under standard conditions, red phosphorus is more stable than white phosphorus, but less stable than the thermodynamically stable black phosphorus. The standard enthalpy of formation of red phosphorus is −17.6 kJ/mol. [3] Red phosphorus is kinetically most stable. Being polymeric, red phosphorus is insoluble in solvents. It shows ...
An even number of protons or neutrons is more stable (higher binding energy) because of pairing effects, so even–even nuclides are much more stable than odd–odd. One effect is that there are few stable odd–odd nuclides: in fact only five are stable, with another four having half-lives longer than a billion years. [citation needed]
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Although both are called "white phosphorus", in fact two different crystal allotropes are known, interchanging reversibly at 195.2 K. [5] The element's standard state is the body-centered cubic α form, which is actually metastable under standard conditions. [4] The β form is believed to have a hexagonal crystal structure. [5]
Dr Brownlie said: “If we do this, we will return 8.5 million tonnes of phosphorus to our farms that could support a food system that could provide enough food for four times our population.