We can determine the neutron number of certain isotope. Selenium is a nonmetal with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. The chemical symbol for Aluminum is Al. Boron is a chemical element with atomic number 5 which means there are 5 protons and 5 electrons in the atomic structure. [120] The resultant high selenium levels in waterways were found to cause congenital disorders in oviparous species, including wetland birds[121] and fish. The chemical symbol for Gadolinium is Gd. The only stable chloride is selenium monochloride (Se2Cl2), which might be better known as selenium(I) chloride; the corresponding bromide is also known. Selenium as a dietary supplement is available in many forms, including multi-vitamins/mineral supplements, which typically contain 55 or 70 µg/serving. The chemical symbol for Curium is Cm. [55][57], The largest commercial use of Se, accounting for about 50% of consumption, is for the production of glass. Consistent with trends indicated by the double bond rule, selenoketones, R(C=Se)R, and selenaldehydes, R(C=Se)H, are rarely observed. This equilibrium also known as “samarium 149 reservoir”, since all of this promethium must undergo a decay to samarium. The chemical symbol for Cobalt is Co. Cobalt is found in the Earth’s crust only in chemically combined form, save for small deposits found in alloys of natural meteoric iron. Representatives of selenides, diselenides, and selenols include respectively selenomethionine, diphenyldiselenide, and benzeneselenol. Selenium's semiconductor properties found numerous other applications in electronics. Rubidium is a soft, silvery-white metallic element of the alkali metal group, with an atomic mass of 85.4678. The chemical symbol for Palladium is Pd. Relative atomic mass: 78.971(8) Selenium was discovered by Jöns Jacob Berzelius (SE) in 1817. Bismuth is a brittle metal with a silvery white color when freshly produced, but surface oxidation can give it a pink tinge. Selenium requirements in plants differ by species, with some plants requiring relatively large amounts and others apparently requiring none. Molybdenum is a chemical element with atomic number 42 which means there are 42 protons and 42 electrons in the atomic structure. The chemical symbol for Silicon is Si. Nobelium is a chemical element with atomic number 102 which means there are 102 protons and 102 electrons in the atomic structure. Thallium is a chemical element with atomic number 81 which means there are 81 protons and 81 electrons in the atomic structure. In 1954, the first hints of specific biological functions of selenium were discovered in microorganisms by biochemist, Jane Pinsent. Tellurium is chemically related to selenium and sulfur. Astatine is a chemical element with atomic number 85 which means there are 85 protons and 85 electrons in the atomic structure. High amount of selenium is also present in oceans . [59] Like lead and sulfur, selenium improves the machinability of steel at concentrations around 0.15%. The atomic mass is the mass of an atom. [46][47], Anthropogenic sources of selenium include coal burning, and the mining and smelting of sulfide ores. Rhodium is a chemical element with atomic number 45 which means there are 45 protons and 45 electrons in the atomic structure. All of its isotopes are radioactive. [92] Evidence suggests that the molecular mechanisms of mercury toxicity includes the irreversible inhibition of selenoenzymes that are required to prevent and reverse oxidative damage in brain and endocrine tissues. 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. Selenium is still used in a few types of DC power surge protectors and one type of fluorescent quantum dot. If you continue to use this site we will assume that you are happy with it. It is the heaviest essential mineral nutrient. It is indicated by the symbol Se and the atomic number of selenium is 34. [125], The Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for selenium in the workplace at 0.2 mg/m3 over an 8-hour workday. Atomic mass of selenium (Se) is 78.96 To find out mass number,we need to round 78.96 to a whole number.So,by rounding,we are getting mass number of selenium (Se) .The mass number of selenium (Se) is 79. Neodymium is a chemical element with atomic number 60 which means there are 60 protons and 60 electrons in the atomic structure. [97], From about three billion years ago, prokaryotic selenoprotein families drive the evolution of selenocysteine, an amino acid. Francium is a chemical element with atomic number 87 which means there are 87 protons and 87 electrons in the atomic structure. [117] Hydrogen selenide is an extremely toxic, corrosive gas. Tellurium is a chemical element with atomic number 52 which means there are 52 protons and 52 electrons in the atomic structure. Argon is mostly used as an inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive; for example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning. [82] There are, however, a few species that have been seen to survive these events and tolerate the increased selenium. It has remarkable resistance to corrosion, even at high temperatures, and is therefore considered a noble metal. Phosphorus is a chemical element with atomic number 15 which means there are 15 protons and 15 electrons in the atomic structure. Tetraselenium tetranitride, Se4N4, is an explosive orange compound analogous to tetrasulfur tetranitride (S4N4). National Research Council, Subcommittee on Sheep Nutrition (1985). The demand for selenium by the electronics industry is declining. Cerium is a soft, ductile and silvery-white metal that tarnishes when exposed to air, and it is soft enough to be cut with a knife. Brazil nuts are the richest dietary source (though this is soil-dependent, since the Brazil nut does not require high levels of the element for its own needs).[106][107]. 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. Oxygen is a chemical element with atomic number 8 which means there are 8 protons and 8 electrons in the atomic structure. ›› Selenium molecular weight. In 1873, Willoughby Smith found that the electrical resistance of grey selenium was dependent on the ambient light. Its use as a photoconductor in plain-paper copiers once was a leading application, but in the 1980s, the photoconductor application declined (although it was still a large end-use) as more and more copiers switched to organic photoconductors. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer (passivation) stabilizes the free metal somewhat against further oxidation. In nuclear industry, especially artificial xenon 135 has a tremendous impact on the operation of a nuclear reactor. Osmium is a chemical element with atomic number 76 which means there are 76 protons and 76 electrons in the atomic structure. 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. Radon occurs naturally as an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead. [49][50] Since its invention, solvent extraction and electrowinning (SX/EW) production of copper produces an increasing share of the worldwide copper supply. Upon heating, it softens at 50 °C and converts to gray selenium at 180 °C; the transformation temperature is reduced by presence of halogens and amines. Another source was the mud from the lead chambers of sulfuric acid plants, a process that is no longer used. Lead is a heavy metal that is denser than most common materials. [75][76][77], 75Se is used as a gamma source in industrial radiography.[78]. The chemical symbol for Holmium is Ho. Europium is a chemical element with atomic number 63 which means there are 63 protons and 63 electrons in the atomic structure. Silicon is a hard and brittle crystalline solid with a blue-grey metallic lustre, it is a tetravalent metalloid and semiconductor. In some respects zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn2+ and Mg2+ ions are of similar size. In humans, selenium is a trace element nutrient that functions as cofactor for reduction of antioxidant enzymes, such as glutathione peroxidases[86] and certain forms of thioredoxin reductase found in animals and some plants (this enzyme occurs in all living organisms, but not all forms of it in plants require selenium). Selenium is not an abundant element. Substantial physiological changes may occur in fish with high tissue concentrations of selenium. The most commonly used spontaneous fission neutron source is the radioactive isotope californium-252. For other isotopes, the isotopic mass usually differs and is usually within 0.1 u of the mass number. Mendelevium is a metallic radioactive transuranic element in the actinide series, it is the first element that currently cannot be produced in macroscopic quantities. Commercially, thallium is produced as a byproduct from refining of heavy metal sulfide ores. E. Discoverer: De Marignac, Charles Galissard, Discoverer: De Marignac, Jean Charles Galissard, Discoverer: Göhring, Otto and Fajans, Kasimir. These have similar chemical properties, but palladium has the lowest melting point and is the least dense of them. The Standard English unit is pounds mass per cubic foot (lbm/ft3). It is also the most corrosion-resistant metal, even at temperatures as high as 2000 °C. It is a nonmetal. Selenium also has numerous unstable synthetic isotopes ranging from 64Se to 95Se; the most stable are 75Se with a half-life of 119.78 days and 72Se with a half-life of 8.4 days. Carbon is a chemical element with atomic number 6 which means there are 6 protons and 6 electrons in the atomic structure. Sheets of amorphous selenium convert X-ray images to patterns of charge in xeroradiography and in solid-state, flat-panel X-ray cameras. Selenium with Atomic Number Z = 34 and Mass Number A = 78.96 is in group VIA and period 4 of the periodic table of the elements. The commercial use of beryllium requires the use of appropriate dust control equipment and industrial controls at all times because of the toxicity of inhaled beryllium-containing dusts that can cause a chronic life-threatening allergic disease in some people called berylliosis. [19] Selenium reacts with fluorine to form selenium hexafluoride: In comparison with its sulfur counterpart (sulfur hexafluoride), selenium hexafluoride (SeF6) is more reactive and is a toxic pulmonary irritant. Erbium is a chemical element with atomic number 68 which means there are 68 protons and 68 electrons in the atomic structure. Chemical element of periodic table. Selenium disulfide has been used in shampoo as an antidandruff agent, an inhibitor in polymer chemistry, a glass dye, and a reducing agent in fireworks. According to the Einstein relationship (E=mc2), this binding energy is proportional to this mass difference and it is known as the mass defect. Density is defined as the mass per unit volume. It is by mass the most common element on Earth, forming much of Earth’s outer and inner core. The metal is found in the Earth’s crust in the pure, free elemental form (“native silver”), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. However, the lack of tellurium compounds in the Falun Mine minerals eventually led Berzelius to reanalyze the red precipitate, and in 1818 he wrote a second letter to Marcet describing a newly found element similar to sulfur and tellurium. When prepared in chemical reactions, selenium is usually an amorphous, brick-red powder. Selenium dichloride is an important reagent in the preparation of selenium compounds (e.g. Other selenium allotropes may contain Se6 or Se7 rings. Another naturally occurring organoselenium compound is dimethyl selenide. The chemical symbol for Radon is Rn. Signs and symptoms of selenosis include a garlic odor on the breath, gastrointestinal disorders, hair loss, sloughing of nails, fatigue, irritability, and neurological damage. 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. China is the dominant consumer of selenium at 1,500–2,000 tonnes/year. Selenium is also found in amino acids in living organisms, where it exists in the form of seleno-methionine, and selenocysteine . Yttrium is a chemical element with atomic number 39 which means there are 39 protons and 39 electrons in the atomic structure. The most common ore of selenium are the sulfide ores. [98] Marine organisms retained and sometimes expanded their selenoproteomes, whereas the selenoproteomes of some terrestrial organisms were reduced or completely lost. The chemical symbol for Xenon is Xe. Selenium is not produced directly by nuclear fusion. Caesium is a soft, silvery-gold alkali metal with a melting point of 28.5 °C, which makes it one of only five elemental metals that are liquid at or near room temperature. Chemically, indium is similar to gallium and thallium. Applications in electronics, once important, have been mostly replaced with silicon semiconductor devices. Atomic Properties; Electronegativity (Pauling scale): 2.55: Atomic Radius: 103 pm: Ionic Radius: 198 pm (-2) Van der Waals Radius: 190 pm: 1st Ionization energy: 941 kJ/mol: 1st Electron affinity:-195 kJ/mol: Oxidation States:-2,2,4,6: Physical Properties; Standard State: solid: Bonding Type: metallic: Melting Point: 494 K: Boiling Point: 958 K: Density: 4.82 g/cm 3: Metal/Non-Metal: nonmetal: Plutonium is a chemical element with atomic number 94 which means there are 94 protons and 94 electrons in the atomic structure. Atomic mass of Selenium is 78.96 u. It is the fourth most common element in the Earth’s crust. [64], Amorphous selenium (α-Se) thin films have found application as photoconductors in flat panel x-ray detectors. Carbon is the 15th most abundant element in the Earth’s crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Thallium is a soft gray post-transition metal is not found free in nature. This smell was not typical of arsenic, but a similar odor was known from tellurium compounds. Discoverer: McMillan, Edwin M. and Abelson, Philip H. Discoverer: Glenn T. Seaborg, Joseph W. Kennedy, Edward M. McMillan, Arthur C. Wohl, Discoverer: Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, Albert Ghiorso, Discoverer: Glenn T. Seaborg, Ralph A. James, Albert Ghiorso, Discoverer: Stanley G. Thompson, Glenn T. Seaborg, Kenneth Street, Jr., Albert Ghiorso, Discoverer: Stanley G. Thompson, Glenn T. Seaborg, Bernard G. Harvey, Gregory R. Choppin, Albert Ghiorso, Discoverer: Albert Ghiorso, Glenn T. Seaborg, Torbørn Sikkeland, John R. Walton, Discoverer: Albert Ghiorso, Torbjørn Sikkeland, Almon E. Larsh, Robert M. Latimer, Copyright 2020 Periodic Table | All Rights Reserved |. Only about 5×10−8% of all matter in the universe is europium. Discoverer: Priestley, Joseph and Scheele, Carl Wilhelm, Discoverer: Ramsay, William and Travers, Morris, Discoverer: Ramsay, Sir William and Strutt, John (Lord Rayleigh), Discoverer: Del Rio, Andrés Manuel (1801) and Sefström, Nils Gabriel (1830), Discoverer: Lecoq de Boisbaudran, Paul-Émile, Discoverer: Ramsay, Sir William and Travers, Morris, Discoverer: Bunsen, Robert Wilhelm and Kirchhoff, Gustav Robert, Discoverer: Perrier, Carlo and Segrè, Emilio, Discoverer: Reich, Ferdinand and Richter, Hieronymus, Discoverer: Müller von Reichenstein, Franz Joseph, Discoverer: Ramsay, William and Travers, Morris William, Discoverer: Kirchhoff, Gustav and Bunsen, Robert. Uranium has the highest atomic weight of the primordially occurring elements. Berkelium is a chemical element with atomic number 97 which means there are 97 protons and 97 electrons in the atomic structure. Dysprosium is used for its high thermal neutron absorption cross-section in making control rods in nuclear reactors, for its high magnetic susceptibility in data storage applications. Atomic Mass of Selenium. Selenium can be refined from these muds by a number of methods. The chemical symbol for Cerium is Ce. Thorium is a chemical element with atomic number 90 which means there are 90 protons and 90 electrons in the atomic structure. Bromine is the third-lightest halogen, and is a fuming red-brown liquid at room temperature that evaporates readily to form a similarly coloured gas. Platinum is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Approximately 60–70% of thallium production is used in the electronics industry. Chemically, sulfur reacts with all elements except for gold, platinum, iridium, tellurium, and the noble gases. [122] Elevated dietary methylmercury levels can amplify the harm of selenium toxicity in oviparous species. But its density pales by comparison to the densities of exotic astronomical objects such as white dwarf stars and neutron stars. On 19 April 2009, 21 polo ponies died shortly before a match in the United States Polo Open. Exceeding the Tolerable Upper Intake Level of 400 micrograms per day can lead to selenosis. Selenium is a chemical element with atomic number 34 which means there are 34 protons and 34 electrons in the atomic structure. If we include man made elements, the densest so far is Hassium. Molybdenum a silvery metal with a gray cast, has the sixth-highest melting point of any element. It is recommended that a water concentration of 2 μg Se/L be considered highly hazardous to sensitive fish and aquatic birds. Selenium is found in metal sulfide ores, where it partially replaces the sulfur. For 12C the atomic mass is exactly 12u, since the atomic mass unit is defined from it. Silicon is a chemical element with atomic number 14 which means there are 14 protons and 14 electrons in the atomic structure. The minimum distance between chains is 343.6 pm. The unit of measure for mass is the atomic mass unit (amu). Connected lines with dots. 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. Praseodymium is the third member of the lanthanide series and is traditionally considered to be one of the rare-earth metals. Germanium is a chemical element with atomic number 32 which means there are 32 protons and 32 electrons in the atomic structure. The information contained in this website is for general information purposes only. Samarium is a chemical element with atomic number 62 which means there are 62 protons and 62 electrons in the atomic structure. One family of selenium-bearing molecules (the glutathione peroxidases) destroys peroxide and repairs damaged peroxidized cell membranes, using glutathione. Nobelium is the tenth transuranic element and is the penultimate member of the actinide series. Since the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance, it is obvious, the density of a substance strongly depends on its atomic mass and also on the atomic number density (N; atoms/cm3). Selenium is a chemical element with the atomic number 34, and is represented by the chemical symbol Se, and has an atomic mass of 78.96. Lead is widely used as a gamma shield. Thorium metal is silvery and tarnishes black when exposed to air, forming the dioxide. A major development was the discovery that steel could be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel. The chemical symbol for Lutetium is Lu. Platinum is a chemical element with atomic number 78 which means there are 78 protons and 78 electrons in the atomic structure. Atomic mass of Selenium is 78.96 u. The chemical symbol for Niobium is Nb. [44][45], Certain soils are selenium-rich, and selenium can be bioconcentrated by some plants. The chemical symbol for Zinc is Zn. The Cookies Statement is part of our Privacy Policy. This color cancels out the green or yellow tints that arise from iron impurities typical for most glass. Liquid nitrogen (made by distilling liquid air) boils at 77.4 kelvins (−195.8°C) and is used as a coolant. Radium is a chemical element with atomic number 88 which means there are 88 protons and 88 electrons in the atomic structure. The atomic mass is the mass of an atom. 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. Their use continued into the 1990s. The chemical symbol for Neon is Ne. The packing is most dense in the α form. The nucleus consists of 34 protons (red) and 46 neutrons (blue). Phytoplankton can concentrate inorganic selenium by a factor of 3000. Nitrogen is a chemical element with atomic number 7 which means there are 7 protons and 7 electrons in the atomic structure. In the human body, selenium content ranges between 1… Selenium (Se). At 0.099%, phosphorus is the most abundant pnictogen in the Earth’s crust. The chemical symbol for Erbium is Er. Tellurium is one … Sign with atomic number and atomic weight. [114] In China, people who ingested corn grown in extremely selenium-rich stony coal (carbonaceous shale) have suffered from selenium toxicity. Despite its high price and rarity, thulium is used as the radiation source in portable X-ray devices. Copper is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. Small amounts of organoselenium compounds have been used to modify the catalysts used for the vulcanization for the production of rubber.[52]. Nearly all technetium is produced synthetically, and only minute amounts are found in the Earth’s crust. Gallium does not occur as a free element in nature, but as gallium(III) compounds in trace amounts in zinc ores and in bauxite. Salts of selenous acid are called selenites. [84] To help reduce the amount of selenium entering our oceans, policies can be put into place such as using microbes or enzymes that target and break down metalloids like selenium. Tin is a chemical element with atomic number 50 which means there are 50 protons and 50 electrons in the atomic structure. Many benthic invertebrates can tolerate selenium concentrations up to 300 μg/L of Se in their diet.[79]. Selenium is a chemical element with symbol Se and atomic number 34. These species are structurally analogous to the corresponding disulfur dichloride. The chemical symbol for Iodine is I. Iodine is the heaviest of the stable halogens, it exists as a lustrous, purple-black metallic solid at standard conditions that sublimes readily to form a violet gas. Curium is a chemical element with atomic number 96 which means there are 96 protons and 96 electrons in the atomic structure. Melting … Lawrencium is the final member of the actinide series. [38][39] In the 1970s, it was shown to be present in two independent sets of enzymes. [65] These detectors use amorphous selenium to capture and convert incident x-ray photons directly into electric charge.[66]. The chemical symbol for Iridium is Ir. Berzelius and Gahn wanted to use the pyrite and they also observed that the red precipitate gave off a smell like horseradish when burned. )[87], Selenium may inhibit Hashimoto's disease, in which the body's own thyroid cells are attacked as foreign. Its extreme rarity in the Earth’s crust, comparable to that of platinum. Promethium is a chemical element with atomic number 61 which means there are 61 protons and 61 electrons in the atomic structure. [99], Trace elements involved in GSH-Px and superoxide dismutase enzymes activities, i.e. Krypton is a chemical element with atomic number 36 which means there are 36 protons and 36 electrons in the atomic structure. Hydrogen is a chemical element with atomic number 1 which means there are 1 protons and 1 electrons in the atomic structure. Gallium is a chemical element with atomic number 31 which means there are 31 protons and 31 electrons in the atomic structure. The size and mass of atoms are so small that the use of normal measuring units, while possible, is often inconvenient. Praseodymium is a soft, silvery, malleable and ductile metal, valued for its magnetic, electrical, chemical, and optical properties. For salmon, the optimal concentration of selenium is about 1 microgram selenium per gram of whole body weight. Its boiling point is the lowest among all the elements. It is occasionally found in native form as elemental crystals. The high bioaccumulation of selenium in aquatic environments cause large fish kills depending on the species in the affected area. The colour ranges from grey metallic to red glassy. Chlorine is a yellow-green gas at room temperature. The chemical symbol for Yttrium is Y. Yttrium is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a “rare-earth element”. Francium is an alkali metal, that has one valence electron. The difference between the neutron number and the atomic number is known as the neutron excess: D = N – Z = A – 2Z. The Atomic Mass and Derivatives of Selenium | Victor Lenher | ISBN: 9781346515083 | Kostenloser Versand für alle Bücher mit Versand und Verkauf duch Amazon. Like the other metals of the platinum group, ruthenium is inert to most other chemicals. Selenium does not exhibit the changes in viscosity that sulfur undergoes when gradually heated.
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