Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesisit is a low-abundance element in the Solar System and in the Earth's crust. These are mined industrially as evaporitessuch as borax and kernite. The largest known boron deposits are in Turkeythe largest producer of boron minerals. Elemental boron is a metalloid that is found in small amounts in meteoroids but chemically uncombined boron is not otherwise found naturally on Earth. Industrially, very pure boron is produced with difficulty because of refractory contamination by carbon or other elements.
Several allotropes of boron exist: amorphous boron is a brown powder; crystalline boron is silvery to black, extremely hard about 9.
The primary use of elemental boron is as boron filaments with applications similar to carbon fibers in some high-strength materials. Boron is primarily used in chemical compounds. About half of all boron consumed globally is an additive in fiberglass for insulation and structural materials. The next leading use is in polymers and ceramics in high-strength, lightweight structural and refractory materials.
Borosilicate glass is desired for its greater strength and thermal shock resistance than ordinary soda lime glass. Boron as sodium perborate is used as a bleach. A small amount of boron is used as a dopant in semiconductorsand reagent intermediates in the synthesis of organic fine chemicals. A few boron-containing organic pharmaceuticals are used or are in study. Natural boron is composed of two stable isotopes, one of which boron has a number of uses as a neutron-capturing agent.
In biology, borates have low toxicity in mammals similar to table saltbut are more toxic to arthropods and are used as insecticides. Boric acid is mildly antimicrobial, and several natural boron-containing organic antibiotics are known. Boron compounds play a strengthening role in the cell walls of all plants.
There is no consensus on whether boron is an essential nutrient for mammals, including humans, although there is some evidence it supports bone health. The word boron was coined from boraxthe mineral from which it was isolated, by analogy with carbonwhich boron resembles chemically.
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Agricola, aroundreports the use of borax as a flux in metallurgy. Inboric acid was recognized in the hot springs soffioni near FlorenceItaly, and became known as sal sedativumwith primarily medical uses.The chemistry of boron more closely resembles the chemistry of silicon silicon, nonmetallic chemical element; symbol Si; at. Click the link for more information. Mendeleev and revised by Henry G. In the periodic table the elements are arranged in columns and rows according to increasing atomic number see the table entitled The chemical reactivity of boron depends on its form; generally, the crystalline form is far less reactive than the amorphous form.
For example, the amorphous powder is oxidized slowly in air at room temperature and ignites spontaneously at high temperatures to form an oxide; the crystalline form is oxidized only very slowly, even at higher temperatures. Boron forms compounds with oxygen, hydrogen, the halogens, nitrogen, phosphorus, and carbon only diamond is harder than boron carbide. It also forms organic compounds. The acids may be thought of as hydrates of boric oxide, B 2 O 3. Boron is used as a deoxidizer and degasifier in metallurgy.
Because it absorbs neutrons, it is used in the shielding material and in some control rods of nuclear reactors. Boron fibers, which have a very high tensile strength, can be added to plastics to make a material that is stronger than steel yet lighter than aluminum. Boron does not occur free in nature. Large deposits of borax, kermite, colemanite, and other boron minerals are found in the arid regions of the W United States.
It occurs also in the mineral tourmaline tourmalinecomplex borosilicate mineral with varying amounts of aluminum, iron, magnesium, sodium, lithium, potassium, and sometimes other elements, used as a gem. It occurs in prismatic crystals, commonly three-sided, six-sided, or nine-sided, and striated vertically. The simplest method of preparing boron is the reduction of boron trioxide by heating with magnesium; this yields the amorphous powder.
Atomic number, 5; atomic weight, Grayish-black crystals. Very pure boron is colorless. Natural boron consists of two stable isotopes: 10 B 19 percent and 11 B 81 percent. Free impure boron was first obtained by the French chemists J. Gay-Lussac and L. Free boron is not found in nature, but many boron compounds are widespread, especially in small concentrations. Boron is a component of many igneous and sedimentary rocks in the form of borosilicates, borates, and boron aluminom silicates, and also as an isomorphic admixture in other minerals.
Boron compounds are found in petroleum waters, sea water, salt lakes, hot springs, volcanic and lava mud, and many soils. Physical and chemical properties. Several crystalline modifications of boron are known. It has been possible by X-ray structural analysis to fully determine the crystalline structure for two of them; in both cases this structure is extremely complex. In these structures, boron atoms form a three-dimensional framework similar to the carbon atoms in diamond; this explains the great hardness of boron.
However, the construction of the boron framework is much more complicated than that of diamond. The basic structural unit in boron crystals is formed by icosahedrons sided figureswith 12 boron atoms in the apex of each one see Figure 1, a.Unops application status longlisted
The icosahedrons are joined both directly Figure 1, b and by means of intermediate boron atoms that are not part ofanyicosahedron Figure 1, c. Since there are only three electrons in the outer shell of the boron atom the electron configuration is 2s 2 2pthere are essentially fewer than two electrons in each bond in crystalline boron.
According to contemporary theories, there is a special type of covalent bond in boron crystals—a multicenter bond with an electron deficit.The three-coordinated derivatives e.
The tetrahedral bonds result from the reception of an unshared pair of electrons from a donor atom—either a neutral molecule or an anion. This allows a variety of structures to form. Solid borates show five types of structures involving several anions i.
Borax has long been used in soaps and mild antiseptics. Because of its ability to dissolve metallic oxides, it has also found wide applications as a soldering flux.
Another boron compound with diverse industrial applications is boric acidH 3 BO 3. This white solidalso called boracic, or orthoboric, acid, is obtained by treating a concentrated solution of borax with sulfuric or hydrochloric acid. Boric acid is commonly used as a mild antiseptic for burns and surface wounds and is a major ingredient in eye lotions.
Among its other important applications are its use as a fire retardant in fabrics, in solutions for electroplating nickel or for tanning leatherand as a major constituent in catalysts for numerous organic chemical reactions.
Upon heating, boric acid loses water and forms metaboric acid, HBO 2 ; further loss of water from metaboric acid results in the formation of boron oxide, B 2 O 3.P Block Video Lecture-4 - Boron Family - Chemistry - NEET \u0026 JEE - VT Sir - Career Point Kota
The latter is mixed with silica to make heat-resistant glass borosilicate glass for use in cooking ware and certain types of laboratory equipment. Boron combines with carbon to form boron carbide B 4 Can extremely hard substance that is used as an abrasive and as a reinforcing agent in composite materials.Mere paas nahi hai koi sath nahi hai song
Boron combines with various metals to form a class of compounds called borides. The borides are usually harder, chemically less reactive, and electrically less resistive and have a higher melting point than the corresponding pure metallic elements.
Boron and compounds
Some of the borides are among the hardest and most heat-resistant of all known substances. Aluminum boride AlB 1 2for example, is used in many cases as a substitute for diamond dust for grinding and polishing. With nitrogenboron forms boron nitride BNwhich, like carbon, can exist in two allomorphic chemically identical but physically different forms. One of them has a layer structure resembling that of graphitewhereas the other has a cubic crystalline structure similar to that of diamond.
The latter allotropic form, called borazon, is capable of withstanding oxidation at much higher temperatures and is extremely hard—properties that make it useful as a high-temperature abrasive. Boron reacts with all halogen elements to give monomeric, highly reactive trihalides BX 3where X is a halogen atom—F, ClBror I. These so-called Lewis acids readily form complexes with amines, phosphines, ethersand halide ions.
Examples of complex formation between boron trichloride and trimethylamine, as well as between boron trifluoride and fluoride ion, are shown in the following equations:. When boron trichloride is passed at low pressure through devices delivering an electric discharge, diboron tetrachloride, Cl 2 B—BCl 2and tetraboron tetrachloride, B 4 Cl 4are formed.
Boron: compounds information
Diboron tetrachloride decomposes at room temperature to give a series of monochlorides having the general formula BCl nin which n may be 8, 9, 10, or 11; the compounds with formulas B 8 Cl 8 and B 9 Cl 9 are known to contain closed cages of boron atoms.
Boron also forms a series of halides with the general formula B n X nwhich also contains closed cages of boron atoms. One example is the boron chloride B 4 Cl 4.Boron is an extremely valuable mineral and it is used in many products from cookware and medicine to nuclear waste storage and space exploration. Boron compounds are mainly used in borosilicate glass products, but are also used in agriculture, in fire retardants, and in soaps and detergents.
Boron is used in special-purpose alloys, in cementation of iron, as oxygen scavenger for copper and other metals, as fibres and filaments in composites with metals or ceramics, as semiconductor, for nuclear reactors, as a shield for nuclear radiation and in instruments used for detecting neutrons. Boron is used in pyrotechnic flares distinctive green colourfor rockets as an igniterin boron-coated tungsten wires and in high temperature brazing alloys.
Borates are used mostly to produce glass. They are also used in fire retardants, leather tanning industries, cosmetics, photographic materials, soaps and cleaners, adhesives and for high-energy fuel. Some pesticides used for cockroach control and some wood preservatives also contain borates. Borax is used in soldering metals, as a cleansing flux in welding, in the manufacture of glazes and enamels e. It is also used for curing and preserving skins, in cockroach control and as a water softener in washing powders.
Boric acid is used for weatherproofing and fireproofing fabrics, as a preservative, in the manufacture of cements, crockery, porcelain, enamels, glass, borates, leather, carpets, hats, soaps, and artificial gems, and in nickel-plating baths. It is also used in the manufacture of cosmetics, in ointments and eye washes, as a mild antiseptic, in printing and dyeing, in photography, for impregnating wicks, for hardening steel, in welding flux, copper brazing, as an insecticide for cockroaches and carpet beetles, and in fungus control for citrus fruits.
Boron oxide is used in metallurgy, in the analysis of silicon dioxide in silicates, in blowpipe analysis, for the production of boron, in heat-resistant glassware, as a fire-resistant additive for paints, in electronics and as an herbicide.
Boron carbide is used as an abrasive, in the manufacture of hard and chemical-resistant ceramics or wear-resistant tools, in the refractory industry, in light weight cermets, in armour tiles, in radiation protection and shielding, in the nuclear industry in control rods in nuclear reactors high capture cross-section to absorb thermal neutronsas raw material for producing other boron containing materials e.
Boron nitride is used as a refractory material, laboratory reagent, and abrasive. Boron trichloride is used in the manufacture and purification of metal alloys, in bonding of iron and steel, in soldering fluxes, and in the manufacture of electrical resistors. It is also used to extinguish magnesium fires in heat resisting furnaces. Boron trifluoride is widely used to promote various organic reactions. Boron filaments are high-strength, lightweight materials that are used in fibre optics research and for advanced aerospace structures.
Boron is a metalloid an element which has both metallic and non-metallic properties that has an odourless, black, hard solid appearance. It can also appear as a brown amorphous powder.
It is a semiconductor. It is extremely difficult to prepare pure boron because of its high melting point and the corrosiveness of the liquid. Borax comes in hard, odourless crystals, granules or powder.Boron Compounds Ltd was established in Recently the Company inaugurated its new dedicated production plant in Ofakim, in the southern region of Israel.
The Company applies a breakthrough technology for the production of pure hexagonal Boron Nitride hBN powders in amorphous and crystalline hexagonal, turbostratic structures in sub-microns and nano particle sizes. Thanks to continuous quality enhancement and sound technical support, Boron Compounds Ltd would be a preferred business partner for clients looking for high quality products at reasonable prices.
Boron Compounds Ltd offers cooperative and efficient customer support to develop products to suit to the most demanding clients' needs and specifications. Who Are We? About Boron Nitride For general information, see here. For further information, see relevant links and articles. Our Products Boron Compounds Ltd supply the Boron Nitride powder in 2 chemical specifications and 3 physical structures.
Contact Us We are at your disposal for any technical and commercials inquries.This proposal may appear to some US politicians to be central planning run amok and it doesn't really address the low pay and social standing of teachers in the United States.Mega truck rear steering
But it does have potential and precedent: an existing programme called Teach for America has succeeded in recruiting thousands of young college graduates to teach in the nation's most troubled neighbourhoods. Other recommendations of note include a call for the creation of a new energy-research agency that would conduct low-cost, high-risk, high-reward research projects.
This would be modelled on the Defense Advanced Research Projects Agency (DARPA), which has been highly successful in backing exciting, basic research that may spawn useful technology.
Another new entity would be set up expressly to arrange for the construction of scientific facilities. It suggests a new category of generous grants that would allow young researchers early in their career to firmly establish their own lines of enquiry. Furthermore, it calls for changes in US immigration policy that would make it easier for foreign students and scientists to stay in the country to continue their careers.
Both these suggestions will require serious political commitment to implement but they would go a long way towards fostering fresh scientific talent. Senators Lamar Alexander (Republican, Tennessee) and Jeff Bingaman (Democrat, New Mexico), who commissioned the study, must now try to drum up support on Capitol Hill for the implementation of its recommendations.
They face an uphill battle, given the size of the US budget deficit and inevitable political resistance to such concepts as further federal involvement in school education. The United States' competitors, in Europe and the Far East, also need to consider such measures, and might actually find some of them easier to implement.
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A very wide range of relaxation techniques have been developed, although many can be seen as variations on a number of basic methods, focusing on the physical feelings of tension, or using mental imagery to induce calm. Perhaps the most powerful method of relaxation is mindfulness. At it's simplest mindfulness is focusing on the current moment, the here and now and allowing, through a type of meditation, worries about the future or regrets about the past to melt away.
See our page on Mindfulness for more information. The symptoms of stress can sometimes be relieved by prescription of medication. Very often such drugs are prescribed to treat the immediate symptoms of stress or to help the sufferer get through a crisis.
Medication will not necessarily address the causes of stress in the long term. Medication may also lead to dependence, if you think you need medication to help with your stress discuss your options carefully with your doctor or other healthcare provider. You should also speak to your doctor if you think you may be depressed. Depression is a serious illness but common and curable, for more information see our pages: What is Depression.
Many people have a great interest in complementary and alternative therapies when attempting to control stress. You may feel that such methods are preferable to more conventional medical approaches. There are many therapies used to deal with stress, including:The SkillsYouNeed Guide to Stress and Stress ManagementLearn more about the nature of stress and how you can effectively cope with stress at work, at home and in life generally.
The Skills You Need Guide to Stress and Stress Management eBook covers all you need to know to help you through those stressful times and become more resilient. Most people suffer from stress at some time in their lives.
An understanding of the causes of stress and learning to avoid stressful situations will help alleviate some of its negative consequences. Some people may also find it useful to use one of the many techniques or other approaches to relaxation to help manage stress themselves.
For information on how to reference correctly please see our page on referencing. QuizOur eBooks:The Skills You Need Concise Guide to LeadershipOur eBooks:The Skills You Need Guide for Students PERSONAL SKILLS Stress and Stress Management Avoiding Stress Search SkillsYouNeed: The SkillsYouNeed Guide to Stress and Stress Management Subscribe to our FREE newsletter and start improving your life in just 5 minutes a day.
Subscribe You'll get our 5 free 'One Minute Life Skills' and our weekly newsletter. We'll never share your email address and you can unsubscribe at any time. See our page: What is Stress. Learn to relax: Many people do not include relaxation time in their schedules. See our section: Relaxation Techniques to learn more.
See our pages: Time Management and Minimising Distractions. See our section: Assertiveness. Ensure that you get enough fun out of life: Plan time in the day to do something that gives you pleasure. See our page: Work-Life Balance. Positive thinking: Do not dwell on failures and reward yourself for your successes.
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