chemical part 34

Although New Zealand soil has low levels of selenium, adverse health effects have not been detected in the residents. Google has many special features to help you find exactly what you're looking for. The only stable chloride is selenium monochloride (Se2Cl2), which might be better known as selenium(I) chloride; the corresponding bromide is also known. Selenium's semiconductor properties found numerous other applications in electronics. The consumption in 2010 was divided as follows: metallurgy – 30%, glass manufacturing – 30%, agriculture – 10%, chemicals and pigments – 10%, and electronics – 10%. Selenium can be refined from these muds by a number of methods. Selenium compounds commonly exist in the oxidation states −2, +2, +4, and +6. The common mineral selenite is not a selenium mineral, and contains no selenite ion, but is rather a type of gypsum (calcium sulfate hydrate) named like selenium for the moon well before the discovery of selenium. Selenium pollution of waterways also occurs when selenium is leached from coal flue ash, mining and metal smelting, crude oil processing, and landfill. [5], Selenium forms several allotropes that interconvert with temperature changes, depending somewhat on the rate of temperature change. [99] About 200 million years ago, new selenoproteins were developed as mammalian GSH-Px enzymes. Previous Article Next Article. [38][39] In the 1970s, it was shown to be present in two independent sets of enzymes. It can also be prepared by ring-opening polymerization of lactide [–C(CH 3)HC(=O)O–] 2, the cyclic dimer of the basic repeating unit. The selenocysteine-containing form occurs in species as diverse as green algae, diatoms, sea urchins, fish, and chickens. COVID-19 is an emerging, rapidly evolving situation. Also, people dependent on food grown from selenium-deficient soil are at risk. The high bioaccumulation of selenium in aquatic environments cause large fish kills depending on the species in the affected area. In June 2015, the US Food and Drug Administration (FDA) published its final rule establishing the requirement of minimum and maximum levels of selenium in infant formula. Other problems include degeneration of liver tissue, swelling around the heart, damaged egg follicles in ovaries, cataracts, and accumulation of fluid in the body cavity and head. Indian Standard. [132], In the regions (e.g. Selenium as a dietary supplement is available in many forms, including multi-vitamins/mineral supplements, which typically contain 55 or 70 µg/serving. [51] This changes the availability of selenium because only a comparably small part of the selenium in the ore is leached with the copper. The minimum distance between chains is 343.6 pm. Selenium is bioaccumulated in aquatic habitats, this results in higher concentrations in organisms than the surrounding water. Commercially, selenium is produced as a byproduct in the refining of these ores, most often during production. [52], Industrial production of selenium usually involves the extraction of selenium dioxide from residues obtained during the purification of copper. [118] The resultant high selenium levels in waterways were found to cause congenital disorders in oviparous species, including wetland birds[119] and fish. 10, 2020 Filed Under: Coronavirus , Industry Tagged With: coronavirus , Daicel , Kao , Shin-Etsu Chemical , Teijin , Tokuyama , Toray 1-Bromoallenes give allenic carbenes under basic conditions, which react with methylindoles to give alkenylquinolines by ring expansion and alkynyl- and allenyl-3H-indoles. It is more acidic than H2S. [64], Amorphous selenium (α-Se) thin films have found application as photoconductors in flat panel x-ray detectors. Michiaki Yamashita, Shintaro Imamura, Md. These data exclude two major producers: the United States and China. Selenium transmits an electric current proportional to the amount of light falling on its surface. [72] Ionized selenium (Se+24) is one of the active mediums used in X-ray lasers. [83], Although it is toxic in large doses, selenium is an essential micronutrient for animals. [36][37] It was discovered to be essential for mammalian life in 1957. Reactions of methylindoles and 2,5-dimethylpyrrole with allenic carbenes . In 1873, Willoughby Smith found that the electrical resistance of grey selenium was dependent on the ambient light. The pyrite from the Falun Mine created a red precipitate in the lead chambers which was presumed to be an arsenic compound, so the pyrite's use to make acid was discontinued. ), woody asters (Xylorhiza sp. Another source was the mud from the lead chambers of sulfuric acid plants, a process that is no longer used. Part 34. In solution it ionizes to HSe−. The sulfoxide in sulfur chemistry is represented in selenium chemistry by the selenoxides (formula RSe(O)R), which are intermediates in organic synthesis, as illustrated by the selenoxide elimination reaction. Hydrogen sulfide reacts with aqueous selenous acid to produce selenium disulfide: Selenium disulfide consists of 8-membered rings. The first commercial products using selenium were developed by Werner Siemens in the mid-1870s. In plants, it occurs as a bystander mineral[clarification needed], sometimes in toxic proportions in forage (some plants may accumulate selenium as a defense against being eaten by animals, but other plants, such as locoweed, require selenium, and their growth indicates the presence of selenium in soil). Browse all issues of Journal of Chemical Research. Get article recommendations from ACS based on references in your Mendeley library. Occupational Safety and Health Administration, National Institute for Occupational Safety and Health, "Atomic weights of the elements 2013 (IUPAC Technical Report)", Magnetic susceptibility of the elements and inorganic compounds, "The NUBASE2016 evaluation of nuclear properties", "Lettre de M. Berzelius à M. Berthollet sur deux métaux nouveaux", "Effect of light on selenium during the passage of an electric current", "The need for selenite and molybdate in the formation of formic dehydrogenase by members of the Coli-aerogenes group of bacteria", "How Selenium Has Altered Our Understanding of the Genetic Code", 10.1579/0044-7447(2007)36[94:SGAH]2.0.CO;2, "How to use the world's scarce selenium resources efficiently to increase the selenium concentration in food", "Public Health Statement: Selenium – Production, Import/Export, Use, and Disposal", "Chemistry: Periodic Table: selenium: key information", "Selenium and Tellurium: Statistics and Information", "Radiography of Welds Using Selenium 75, Ir 192 and X-rays", "Aquatic selenium pollution is a global environmental safety issue", "Mercury, selenium and fish oils in marine food webs and implications for human health", "Review of selenium toxicity in the aquatic food chain", Linus Pauling Institute at Oregon State University, "Dietary and tissue selenium in relation to methylmercury toxicity", "Post-transcriptional defects of antioxidant selenoenzymes cause oxidative stress under methylmercury exposure", "Protective effect of selenite against methylmercury toxicity: observations concerning time, dose and route factors in the development of selenium attenuation", "Inhibition of the human thioredoxin system: A molecular mechanism of mercury toxicity", Strong antioxidant activity of the novel selenium-containing imidazole compound ″selenoneine″, "Discovery of the strong antioxidant selenoneine in tuna and selenium redox metabolism", "Mercury: selenium interactions and health implications", "Selenocysteine-containing proteins in mammals", "Evolutionary dynamics of eukaryotic selenoproteomes: large selenoproteomes may associate with aquatic life and small with terrestrial life", "Evolution of Dietary Antioxidant Defences", "Reconsidering the evolution of eukaryotic selenoproteins: a novel nonmammalian family with scattered phylogenetic distribution", "The microbial selenoproteome of the Sargasso Sea", "FDA Issues Final Rule to Add Selenium to List of Required Nutrients for Infant Formula", "Dietary Supplement Fact Sheet: Selenium", "Public Health Statement: Health Effects", "Polo pony selenium levels up to 20 times higher than normal", "A teratogenic deformity index for evaluating impacts of selenium on fish populations", "CDC - NIOSH Pocket Guide to Chemical Hazards - Selenium", "Effect of micronutrient status on natural killer cell immune function in healthy free-living subjects aged ≥90 y", "Selenium and iodine supplementation of rural Tibetan children affected by Kashin-Beck osteoarthropathy", National Institutes of Health page on Selenium, CDC - NIOSH Pocket Guide to Chemical Hazards, https://en.wikipedia.org/w/index.php?title=Selenium&oldid=999381397, Biology and pharmacology of chemical elements, Articles with dead external links from November 2020, Short description is different from Wikidata, Wikipedia articles needing clarification from August 2018, Wikipedia articles needing clarification from November 2015, Articles with unsourced statements from June 2016, Pages using Sister project links with hidden wikidata, Creative Commons Attribution-ShareAlike License, grey metallic-looking, red, and vitreous black (not pictured) allotropes, This page was last edited on 9 January 2021, at 22:00. Watch Chemistry Chemical Bonding part 34 (Numerical) CBSE class 11 XI - dogbzock on Dailymotion Another selenium-bearing enzyme in some plants and in animals (thioredoxin reductase) generates reduced thioredoxin, a dithiol that serves as an electron source for peroxidases and also the important reducing enzyme ribonucleotide reductase that makes DNA precursors from RNA precursors. Selenium dioxide is formed by the reaction of elemental selenium with oxygen:[6], It is a polymeric solid that forms monomeric SeO2 molecules in the gas phase. Further concentration through bioaccumulation occurs along the food chain, as predators consume selenium rich prey. [137], It has been suggested that selenium supplementation may help prevent cancer incidence in people, but research has established there is no evidence to support such claims. National Research Council, Committee on Nutrient Requirements of Small Ruminants (2007). Because of its similarity to tellurium, named for the Earth, Berzelius named the new element after the Moon.[26][27]. Illustrative selenides include mercury selenide (HgSe), lead selenide (PbSe), zinc selenide (ZnSe), and copper indium gallium diselenide (Cu(Ga,In)Se2). [6], Analogous to the behavior of other chalcogens, selenium forms hydrogen selenide, H2Se. Signs and symptoms of selenosis include a garlic odor on the breath, gastrointestinal disorders, hair loss, sloughing of nails, fatigue, irritability, and neurological damage. [12] The non-primordial radioisotope 79Se also occurs in minute quantities in uranium ores as a product of nuclear fission. If you have access to a journal via a society or association membership, please browse to your society journal, select an article to view, and follow the instructions in this box. [42][43] Ocean water contains significant amounts of selenium. Representatives of selenides, diselenides, and selenols include respectively selenomethionine, diphenyldiselenide, and benzeneselenol. [56], During the electrowinning of manganese, the addition of selenium dioxide decreases the power necessary to operate the electrolysis cells. ), and false goldenweed (Oonopsis sp. In Belews Lake North Carolina, 19 species of fish were eliminated from the lake due to 150-200 μg Se/L wastewater discharged from 1974 to 1986 from a Duke Energy coal-fired power plant. Consistent with trends indicated by the double bond rule, selenoketones, R(C=Se)R, and selenaldehydes, R(C=Se)H, are rarely observed. pH-dependent plant pigments that can be used as pH indicators occur in many plants, including hibiscus, red cabbage (anthocyanin), and grapes ().The juice of citrus fruits is acidic mainly because it contains citric acid.Other carboxylic acids occur in many living systems. Selenium was also recognized as an important veterinary toxin, which is seen in animals that have eaten high-selenium plants. Five of these, 74Se, 76Se, 77Se, 78Se, 80Se, are stable, with 80Se being the most abundant (49.6% natural abundance). The packing is most dense in the α form. Native (i.e., elemental) selenium is a rare mineral, which does not usually form good crystals, but, when it does, they are steep rhombohedra or tiny acicular (hair-like) crystals. Chemical Watch empowers our members to transform product safety management and unlock the full value of regulatory compliance within their business. Selenium does not exhibit the changes in viscosity that sulfur undergoes when gradually heated. Other selenium allotropes may contain Se6 or Se7 rings. Selenium is a component of the unusual amino acids selenocysteine and selenomethionine. [58], Selenium is used with bismuth in brasses to replace more toxic lead. Minerals that are pure selenide or selenate compounds are known but rare. [115] Hydrogen selenide is an extremely toxic, corrosive gas. [6][8], Owing to its use as a photoconductor in flat-panel x-ray detectors (see below), the optical properties of amorphous selenium (α-Se) thin films have been the subject of intense research.[9][10][11]. Selenium is still used in a few types of DC power surge protectors and one type of fluorescent quantum dot. Sodium is the principal cation of the extracellular fluid and plays a large part in fluid and electrolyte replacement therapies. At levels of 1 mg/m3, selenium is immediately dangerous to life and health. Selenium dichloride is an important reagent in the preparation of selenium compounds (e.g. [110] This 400 µg Tolerable Upper Intake Level is based primarily on a 1986 study of five Chinese patients who exhibited overt signs of selenosis and a follow up study on the same five people in 1992. [12] Isotopes lighter than the stable isotopes primarily undergo beta plus decay to isotopes of arsenic, and isotopes heavier than the stable isotopes undergo beta minus decay to isotopes of bromine, with some minor neutron emission branches in the heaviest known isotopes. [117], Selenium poisoning of water systems may result whenever new agricultural runoff courses through normally dry, undeveloped lands. However, it can damage plants at higher doses. [6][21][22] It can be synthesized by the reaction of selenium tetrachloride (SeCl4) with [((CH3)3Si)2N]2Se. Alkali metal selenides react with selenium to form polyselenides, Se2−n, which exist as chains. [86], Increased dietary selenium reduces the effects of mercury toxicity,[87][88][89] although it is effective only at low to modest doses of mercury. The chief commercial uses for selenium today are glassmaking and pigments. [63] The Li–Se battery is an alternative to the lithium–sulfur battery, with an advantage of high electrical conductivity. [15], Selenium trioxide may be synthesized by dehydrating selenic acid, H2SeO4, which is itself produced by the oxidation of selenium dioxide with hydrogen peroxide:[17], Hot, concentrated selenic acid can react with gold to form gold(III) selenate.[18]. Part 34. Selenium is most commonly found as an impurity, replacing a small part of the sulfur in sulfide ores of many metals. For example, lactic acid is produced by muscle activity. )[85], Selenium may inhibit Hashimoto's disease, in which the body's own thyroid cells are attacked as foreign. Selenium rectifiers were first used in 1933. Selenium is a chemical element with the symbol Se and atomic number 34. These species are structurally analogous to the corresponding disulfur dichloride. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic.It rarely occurs in its elemental state or as pure ore compounds in the Earth's crust. [33][34][35] These lasted in commercial applications until the 1970s, following which they were replaced with less expensive and even more efficient silicon rectifiers. In low doses, selenium has shown a beneficial effect on plant resistance to various environmental stress factors including drought, UV-B, soil salinity, and cold or hot temperatures. [109], Although selenium is an essential trace element, it is toxic if taken in excess. Another naturally occurring organoselenium compound is dimethyl selenide. [7], The most stable and dense form of selenium is gray and has a hexagonal crystal lattice consisting of helical polymeric chains, where the Se-Se distance is 237.3 pm and Se-Se-Se angle is 130.1° . Much below that level, young salmon die from deficiency;[124] much above, they die from toxic excess. The demand for selenium by the electronics industry is declining. These materials are semiconductors. Selenium is a semiconductor and is used in photocells. [82] It has also been suggested that season could have an impact on the harmful effects of selenium on fish. [81] With so many humans consuming fish as a source of protein, it is important to be aware of the selenium pollution occurring in the oceans they get their fish from so we know what we are putting in our bodies. [44][45], Certain soils are selenium-rich, and selenium can be bioconcentrated by some plants. Some analytical techniques are capable of distinguishing organic from inorganic forms of the element. Selenium-specific supplements typically contain either 100 or 200 µg/serving. Zinc selenide was the first material for blue LEDs, but gallium nitride dominates that market. Exceeding the Tolerable Upper Intake Level of 400 micrograms per day can lead to selenosis. [55], Researchers found that application of selenium fertilizer to lettuce crops decreased the accumulation of lead and cadmium. Selenium poisoning can be passed from parents to offspring through the egg, and selenium poisoning may persist for many generations. Access to society journal content varies across our titles. Selenous acid is bubbled with sulfur dioxide (reduction step) to give elemental selenium. Further studies are needed to confirm these interactions. In X-ray crystallography, incorporation of one or more selenium atoms in place of sulfur helps with multiple-wavelength anomalous dispersion and single wavelength anomalous dispersion phasing. It is recommended that a water concentration of 2 μg Se/L be considered highly hazardous to sensitive fish and aquatic birds. When rapidly melted, it forms the black, vitreous form, usually sold commercially as beads. [114] Elemental selenium and most metallic selenides have relatively low toxicities because of low bioavailability. #Class 7 #Standard 7 # Changes: Physical and Chemical #General Science # Maharashtra State Board Substantial physiological changes may occur in fish with high tissue concentrations of selenium. Coronavirus Report – Part 34: Chemical Companies to Continue Operations as Japan Declares State of Emergency Apr. Structures of the toxisterols 2. Adult fish may appear healthy despite their inability to produce viable offspring. [95], From about three billion years ago, prokaryotic selenoprotein families drive the evolution of selenocysteine, an amino acid. Though once widely used, selenium rectifiers have mostly been replaced (or are being replaced) by silicon-based devices. This phenomenon was used in the design of light meters and similar devices. [75][76][77], 75Se is used as a gamma source in industrial radiography.[78]. Selenium is a chemical element with the symbol Se and atomic number 34. [82] There are, however, a few species that have been seen to survive these events and tolerate the increased selenium. Also naturally occurring is the long-lived primordial radionuclide 82Se, with a half-life of 9.2×1019 years. In 1954, the first hints of specific biological functions of selenium were discovered in microorganisms by biochemist, Jane Pinsent. A few of these appeared more recently, in the last 50–200 million years, in fruits and flowers of angiosperm plants. Michael H. Abraham, Jenik Andonian-Haftvan, Gary S. Whiting, Albert Leo and Robert S. Taft Abstract. For other applications, a red color may be desired, produced by mixtures of CdSe and CdS. [120] Elevated dietary methylmercury levels can amplify the harm of selenium toxicity in oviparous species. High doses of Se supplements in pregnant animals might disturb the Zn:Cu ratio and lead to Zn reduction; in such treatment cases, Zn levels should be monitored.

Ark Forest Titan Items, You All Eat In German, Fake Eureka Carts 2020, Quilters Select Cutting Mat 36x60, Drew Parcell Net Worth 2019, Ark Investment Management, All Terrain Manual Wheelchair,