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The isotope selenium-75 has radiopharmaceutical uses. For example, it is used in high-dose-rate endorectal brachytherapy, as an alternative to iridium-192. [8]In paleobiogeochemistry, the ratio in amount of selenium-82 to selenium-76 (i.e, the value of δ 82/76 Se) can be used to track down the redox conditions on Earth during the Neoproterozoic era in order to gain a deeper understanding of ...
Selenium is a chemical element; it has the symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elemental state or as pure ore compounds in Earth's crust.
Allotropy. Property of some chemical elements to exist in two or more different forms. 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 ...
The van der Waals radius, r w, of an atom is the radius of an imaginary hard sphere representing the distance of closest approach for another atom. It is named after Johannes Diderik van der Waals, winner of the 1910 Nobel Prize in Physics, as he was the first to recognise that atoms were not simply points and to demonstrate the physical consequences of their size through the van der Waals ...
Atomic radii of the elements (data page) The atomic radius of a chemical element is the distance from the center of the nucleus to the outermost shell of an electron. Since the boundary is not a well-defined physical entity, there are various non-equivalent definitions of atomic radius. Depending on the definition, the term may apply only to ...
The red allotrope converts to the black allotrope in the presence of heat. The gray allotrope of selenium is made from spirals on selenium atoms, while one of the red allotropes is made of stacks of selenium rings (Se 8). [2] [dubious – discuss] Tellurium is not known to have any allotropes, [24] although its typical form is hexagonal ...
For US food and dietary supplement labeling purposes, the amount in a serving is expressed as a percent of Daily Value (%DV). For selenium labeling purposes, 100% of the Daily Value was 70 μg, but as of 27 May 2016 it was revised to 55 μg. [34] [35] A table of the old and new adult daily values is provided at Reference Daily Intake.
Infobox references. Copper selenide is an inorganic binary compound between copper and selenium. The chemical formula depends on the ratio between the two elements, such as CuSe or Cu 2 Se. The crystalline structure and electronic behavior is determined by its elemental composition. [2] Stoichiometric copper selenide is a zero bandgap material ...