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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.
Glassy carbon or vitreous carbon is a class of non-graphitizing carbon widely used as an electrode material in electrochemistry, as well as for high-temperature crucibles and as a component of some prosthetic devices. It was first produced by Bernard Redfern in the mid-1950s at the laboratories of The Carborundum Company, Manchester, UK.
Phosphorus reacts with oxygen, usually forming two oxides depending on the amount of available oxygen: P 4 O 6 (phosphorus trioxide) when reacted with a limited supply of oxygen, and P 4 O 10 when reacted with excess oxygen. On rare occasions, P 4 O 7, P 4 O 8, and P 4 O 9 are also formed, but in small amounts.
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At least five allotropes are uniquely formed at high pressures, two of which are metallic. [6] The number of sulfur allotropes reflects the relatively strong S−S bond of 265 kJ/mol. [1] Furthermore, unlike most elements, the allotropes of sulfur can be manipulated in solutions of organic solvents and are analysed by HPLC. [7]
Iron allotropes, showing the differences in structure. The alpha iron (α-Fe) is a body-centered cubic (BCC) and the gamma iron (γ-Fe) is a face-centered cubic (FCC). At atmospheric pressure, three allotropic forms of iron exist, depending on temperature: alpha iron (α-Fe, ferrite), gamma iron (γ-Fe, austenite), and delta iron (δ-Fe).
The number of organic compounds is immense and the known number of defined compounds is close to 10 million. [4] However, an indefinitely large number of such compounds is theoretically possible. By definition, an organic compound must contain at least one atom of carbon, but this criterion is not generally regarded as sufficient.
Most atoms form B 12 discrete icosahedra; a few form partially interpenetrating icosahedra, and there are two deltahedral B 10 units, and a single central B atom. [32] For a long time, it was unclear whether the α or β phase is most stable at ambient conditions; however, gradually a consensus was reached that the β phase is the most ...