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Monoclinic phosphorus, violet phosphorus, or Hittorf's metallic phosphorus is a crystalline form of the amorphous red phosphorus. [14] [15] In 1865, Johann Wilhelm Hittorf heated red phosphorus in a sealed tube at 530 °C. The upper part of the tube was kept at 444 °C. Brilliant opaque monoclinic, or rhombohedral, crystals sublimed as a result.
Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in crystalline structure.. Allotropy or allotropism (from Ancient Greek ἄλλος (allos) 'other' and τρόπος (tropos) 'manner, form') is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements.
Phosphorus has several allotropes that exhibit strikingly diverse properties. [11] The two most common allotropes are white phosphorus and red phosphorus. [12] For both pure and applied uses, the most important allotrope is white phosphorus, often abbreviated WP. White phosphorus is a soft, waxy molecular solid composed of P 4 tetrahedra. This P
Hittorf's phosphorus, or violet phosphorus, is one of the crystalline forms of red phosphorus. [20] [7] It adopts the following structure: Hittorf's phosphorus chain structure Hitorff's phosphorus crystal structure. Violet phosphorus can be prepared by sublimation of red phosphorus in a vacuum, in the presence of an iodine catalyst. [7]
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]
For elements that have multiple allotropes, the reference state usually is chosen to be the form in which the element is most stable under 1 bar of pressure. One exception is phosphorus, for which the most stable form at 1 bar is black phosphorus, but white phosphorus is chosen as the standard reference state for zero enthalpy of formation. [2]
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Pages in category "Allotropes" The following 23 pages are in this category, out of 23 total. ... Allotropes of phosphorus; Allotropes of plutonium; R. Red phosphorus ...