Understanding The Chemistry Of Nickel

Understanding The Chemistry Of Nickel Nickel is silvery white [1] and lustrous metal. It is the 7th most abundant transition metal and 24th most abundant element in the crust of earth. It has an atomic number of 28, atomic mass of 58.71 gmol-1 and atomic volume of 6.59 cm3mol-1 [2]. It belongs to group 10 (8B) and 4th period of modern periodic table. Nickel has electronic configuration [Ar] 4s2 3d8 [3]. It has property of malleability and ductility. 300 kilometers long wire can be drawn from a single kilogram of nickel. It has high electrical and thermal conductivities of 0.146 x 106 Scm-1 and 90.9 Wm-1K-1. It is hard, odorless and corrosion resistant metal that takes a high polish. Nickel crystallizes with face centered cubic structure. The unit cell has lattice parameter of 0.352 nm with atomic radius of 0.124 nm. Nickel is naturally occuring ferro magnetic and magnetostrictive material [4] at or near room temperature. Its curie temperature is 355  °C [5]. Nickel is mined from two types of ore deposits. These include laterites and sulphides. Laterites are silicate or oxide ores. It occurs most usually in combination with sulfur and iron in pentlandite (NiS.2FeS) which contains 1.5% nickel, with sulfur in millerite (NiS), with arsenic in mineral nickeline (NiAs) as a red nickel ore, containing 43.9% nickel and 56.1% arsenic, and with arsenic and sulfur in nickel glance [6]. 1.2 Chemical Properties of Nickel Nickel is relatively unreactive element. Under ambient conditions, it does not react with water, oxygen or dissolve in most acids. 1.2.1 Standard Reduction Potentials In aqueous solution, the standard reduction potentials for various oxidation states of nickel are shown in Scheme 1.1 [7, 8]. Scheme 1.1 Standard Electrode Potentials of Various Nickel Species 1.2.2 Reaction of Nickel with Halogens Nickel dichloride, NiCl2, nickel dibromide, NiBr2, and nickel diiodide, NiI2, are formed by the reactions of nickel with chlorine, Cl2, bromine, Br2, and iodine, I2. Ni(s) + Cl2(g) à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ NiCl2(s) (yellow) Ni(s) + Br2(g) à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ NiBr2(s) (yellow) Ni(s) + I2(g) à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ NiI2(s) (black) 1.2.3 Reaction of Nickel with Acids Nickel metal dissolves slowly in dilute sulphuric acid to form solution containing the aquated Ni(II) ion together with hydrogen gas, H2. Ni(s) + H2SO4(aq) à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ Ni2+(aq) + SO42-(aq) + H2(g) Ni(s) + HCl(aq) à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ Ni2+(aq) + Cl- (aq) + H2(g) It does not dissolve in concentrated nitric acid, HNO3, because it is rendered passive by this reagent [9]. 1.2.4 Reaction of Nickel with Air Nickel in finely divided form reacts readily with air. At higher temperatures, it burns in oxygen to form nickel oxide. 2Ni(s) + O2(g) à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ 2NiO(s) 1.3 Oxidation States The oxidation states of nickel include -1, 0, +1, +2, +3 or +4. The most prevalent oxidation state is +2, but compounds of Ni0, Ni+1, and Ni3+ are well known. Ni4+ has also been demonstrated [10]. 1.4 Nickel(II) Compounds Nickel is known primarily for its divalent compounds with all common anions, i.e. halides, hydroxide, sulfate, carbonate, carboxylates, sulfide and hydroxide. Green and blue are the characteristic colors of its compounds. Important nickel(II) compounds include: 1.4.1 Oxides Nickel oxide, NiO is a powdery green solid that becomes yellow on heating [11]. It can be prepared easily by heating nickel carbonate, nitrate or hydroxide. 1.4.2 Sulfides Nickel sulfides occur in different forms such as NiS, nickel sulphide, NiS2, nickel persulphide and Ni3S2, trinickel disulphide. 1.4.3 Halides NiCl2 is yellow but NiCl2.6H2O is of green colour. NiCl2 is prepared by NiCl2.6H2O + 6SOCl2 à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ NiCl2 + 6SO2 + 12HCl NiF2 is prepared by treatment of anhydrous nickel(II) chlHYPERLINK http://en.wikipedia.org/wiki/Nickel(II)_chlorideoride with fluorine at 350  °C [12]. NiClHYPERLINK http://en.wikipedia.org/wiki/Nickel(II)_chloride2 + FHYPERLINK http://en.wikipedia.org/wiki/Fluorine2 à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ NiF2 + ClHYPERLINK http://en.wikipedia.org/wiki/Chlorine2 1.4.4 Nitrates Nickel(II) nitrate hexahydrate, Ni(NO3)2.6H2O is highly soluble in water, giving emerald green solutions. 1.4.5 Carbonates Nickel(II) carbonate is a pale green polymeric solid consisting of Ni2+ cations and [COHYPERLINK http://en.wikipedia.org/wiki/Carbonate3HYPERLINK http://en.wikipedia.org/wiki/Carbonate]HYPERLINK http://en.wikipedia.org/wiki/Carbonate2- anions. It is readily decomposed by aqueous acids to give solutions containing the ion [Ni(H2O)6]2+, liberating water and carbon dioxide. 1.4.6 Sulfates The anhydrous form has a yellow to green color while NiSO4.7H2O and NiSO4.6H2O appears green and blue to pale green, respectively. 1.4.7 Hydroxides Ni(OH)2 occurs as green crystals that can be precipitated when aqueous alkali is added to a solution of nickel (II) salt. Its decomposition on heating above 230  °C produces toxic gases. 1.5 Nickel (III), Nickel (IV) Nickel (VI) Compounds The +3 oxidation state is found in dinickel trioxide, Ni2O3. NiO4-2 is an example of +6 oxidation state while NiO2 and NiF6-2 correspond to +4 oxidation states. Nickel(IV) also occurs in BaNiO3 and in the periodate salts, MNiIO6 (M = alkali cation, NH4). 1.6 Water Soluble, Poorly Soluble Insoluble Nickel Compounds In contrast to water soluble nickel salts (chloride, nitrate, acetate and sulfate), metallic nickel, nickel sulfides, and nickel oxides are poorly soluble in water [13]. NiCO3 is partly water soluble. 1.7 Nickel(II) Complexes Nickel in its most common +2 oxidation state displays a wider range of geometries in its complexes than any other metal ion with coordination numbers 3 to 6. Nickel(II) forms many complexes with octahedral [14, 15], square planar [16, 17, 18] and tetrahedral [19, 20] geometries and a smaller number of five coordinate compounds [21, 22] with square pyramidal and trigonal bipyramidal arrangements. Nickel(II) octahedral, trigonal bipyramidal, square pyramidal and tetrahedral complexes are paramagnetic and have in the majority of cases a green or blue colour. The square planar nickel complexes are diamagnetic and mostly have a yellow, red or brown colour. The ligand exchange processes for nickel(II) tend to be associative, while with palladium(II) and platinum(II), dissociative pathways predominate which tends to adopt only square planar complexes. 1.7.1 Six Coordinate Octahedral Nickel(II) Complexes Nickel(II) forms octahedral complexes with neutral ligands such as H2O and NH3. Amines displace some or all of water molecules in the octahedral [Ni(H2O)6]2+ ion to form complexes such as trans [Ni(H2O)2(NH3)4]2+, [Ni(NH3)6]2+ and [Ni(en)3]2+. These complexes are characteristically purple or blue in contrast to the bright green hexaaquanickel(II) ion, [Ni(H2O)6]2+ [23]. These octahedral complexes have two unpaired electrons and are paramagnetic with magnetic moments 2.9 to 3.4 BM. Other examples include dichlorobis(ethylenediamine)nickel(II), a blue solid, soluble in water and polar organic solvents [24] and Ni(acac)2.2H2O [25]. 2+ 2+ [Ni(H2O)6]2+ [Ni(NH3)6]2+ Ni(en)2Cl2 Ni(acac)2.2H2O 1.7.2 Five Coordinate Square Pyramidal Trigonal Bipyramidal Nickel(II) Complexes Several phosphine and arsine ligands form five coordinate trigonal bipyramidal complexes because tetradentate tripod ligands such as N[C2H4N(CH3)2]3 and N[C2H4PPh2]3 cannot span the apices of a regular tetrahedron. One face is left open for 5th ligand, e.g halide ion to form trigonal bipyramidal complex. Though hydride, thiolate, alkyl and other anionic ligands are also known; the complexes are therefore +1 cations. Tris(1,3-diaminopropane) chromium(III) pentacyanonickelate(II), [Cr(tn)3][Ni(CN)5] has square pyramidal [Ni(CN)5]3- anions. In contrast, crystalline tris(ethylenediamine) chromium(III) pentacyanonickelate(II) sesquihydrate, [Cr(en)3][Ni(CN)5].1.5H2O contains both square pyramidal anions and slightly distorted trigonal bipyramidal anions [26]. The trigonal bipyramidal structure is favored on the basis of ligand repulsion alone. For this reason, almost every five coordinate compound having non metallic central element such as PF5 has trigonal bipyramidal structure unless there are lone pairs. 1.7.3 Four Coordinate Nickel(II) Complexes Nickel(II) in its four coordination mode exhibits either tetrahedral or square planar geometry. 1.7.3.1 Tetrahedral Nickel(II) Complexes Nickel(II) tetrahedral complexes of stoichiometric types; NiX42-, NiX3L-, NiL2X2 and Ni(L-L)2 are known where X represents halogen, L is neutral ligand such as phosphine, phosphine oxide or arsine, and L-L is bidentate ligand such as ethylenediamine. Tetrahedral arrangement for Ni2+ will be preferred if the ligands are large and weak field. Ni(PPh3)3Cl NiCl42- [Ni(acac)2] 1.7.3.2 Square Planar Nickel(II) Complexes For the vast majority of four coordinate nickel(II) complexes, planar geometry is preferred for small and strong field ligands. Tetracyanonickelate(II) will probably be orange red colored square planar complex. Almost all planar complexes of nickel(II) with d8 configuration are diamagnetic. Important examples of square planar complexes are red bis(dimethylglyoximato) nickel(II) [27] and dichloro[1,3-bis(diphenylphosphino)propane]nickel, NiCl2(dppp). Ni(dmgH)2 NiCl2(dppp) [Ni(C2O4)2]2- [Ni(CN)4]2- 1.7.4 Three Coordinate Nickel(II) Complexes There are many examples of trigonal complexes for nickel(0), however, they are rare for Ni(II). The examples include dialkylamides [Ni(NR2)3]1- and Ni2(  µ-NR2)2(NR2)2 as well as blue mesityl complex [Ni(mes)3]1- which has approximately T shaped geometry [28, 29]. 1.8 Nickel(III) Complexes [Ni(tdt)2]- is nickel(III) square planar complex anion having coordination number four where tdt = 3,4-toluenedithiole. Other examples include [Ni(tacn)2]3+ with 1,4,7-triazacyclononane [30] and dark green air stable Ni(III) complex having donor NO2S2 chromophore [31]. Ni[(NO2S)2(C6H4)4] [Me(tdt)2]-, Me = Ni [Ni(tacn)2]3+ 1.9 Nickel(IV) Complexes A well established bis chelated complex of nickel(IV) is the diacetylpyridine dioximato complex [32]. Other examples include dicarbollide complex, Ni(closo-1,2-C2B9H11)2 [33] and the polyselenide anion [Ni4Se4(Se3)(Se4)]4- with a cubic Ni4Se4 core [34]. The hexadentate ligand 3,14-dimethyl-4,7,10,13-tetraazahexadeca-3,13-diene 2,15-dione dioxime forms pseudooctahedral NiN6 complex with nickel(IV) [35]. 1.10 Nickel(-I, 0, +I) Complexes The low valent oxides, K3[NiO2] and KNa2[NiO2] contain linear [O-Ni(I)-O]3- units [36]. The majority of nickel(I) complexes contain phosphine ligands and have tetrahedral or trigonal bipyramidal structure. They are paramagnetic as expected for d9 configurations. In Ni(CO)4, nickel is in zero oxidation state [37]. Bis(cyclooctadiene)nickel(0), Ni(C8H12)2 is a diamagnetic featuring tetrahedral nickel(0) [38]. Ni(cod)2 Ni(CO)4 1.11 Biological Role Nickel is a part of urease. [NiFe]-hydrogenases selectively oxidise H2. Carbon monoxide dehydrogenase enzymes consists of Fe-Ni-S cluster [39]. Other nickel containing enzymes include class of superoxide dismutase and glyoxalase [40]. Enzymatic reactions depend on redox activity of nickel atoms in enzymes active site. In fact, proposed mechanisms of NiFe hydrogenase [41], methyl-CoM reductase [42, 43] and NiSOD [44, 45] involves reduced (Nio, Ni+) and or oxidized (Ni3+) forms of nickel. Nickel along with iron plays vital role in transport of oxygen in blood. Nickel also acts as co-factor in absorption of iron from intestine. 1.12 Sources and Potential Exposure of Nickel Nickel is a ubiquitous natural trace element and it occurs in air, water and soil of the biosphere [46]. 1.12.1 Diet Food and drinking water [47, 48] are the major sources of nickel exposure [49]. Fats, chocolates [50], nuts, candies [51], tomatoes, bananas, onions, spinach, legumes, tea [52], white flour and all canned foods [53] are rich in nickel content. 1.12.2 Ambient Air Nickel oxide, nickel chloride, nickel carbonyl and nickel subsulphide are inhaled pollutants. Nickel levels in ambient air are in range 1 10 ng/m3 in urban areas, although much higher levels 110 180 ng/m3 have been recorded in heavily industrialized areas and larger cities [54]. 1.12.3 Tobacco Smoking It is major source of nickel in indoor air. A cigarette contains 1 3  µg of nickel. Nickel in a burning cigarette form nickel tetracarbonyl that is volatile and gaseous compound and badly affects respiratory tract [55]. 1.12.4 Occupational Exposure of Nickel Pulmonary absorption is major route of nickel exposure in industries [56]. The general population is also exposed to nickel in nickel alloys and nickel plated materials such as coins [57], jewellery [58], electric guitar strings [59], stainless steel cutlery, soaps and detergents. 1.13 Exposure Limits of Nickel The American Conference of Governmental and Industrial Hygienists (ACGIH) has assigned threshold limit value time weighted average for exposure to nickel compounds is 1.5 mg/m3 for elemental nickel, 0.1 mg/m3 for soluble inorganic nickel compounds and nickel subsulfide, 0.2 mg/m3 for insoluble inorganic compounds and 0.05 ppm for nickel carbonyl [60]. 1.14 Toxicity of Nickel Nickel is known as haemato, immunoto, neuro, geno, reproductive, pulmonary toxic and carcinogenic agent. 1.14.1 Acute Toxicity (01 day) The accidental inhalation of nickel carbonyl causes acute toxic effects in two stages, immediate and delayed. The immediate symptoms include headache, vertigo, irritability, which usually last a few hours, followed by an asymptomatic interval of 12 h to 5 days. The delayed symptoms are: 1.14.1.1 Nickel Itch Soluble nickel compounds on skin contact may result in nickel itch [61], most frequently when skin is moist. 1.14.1.2 Gastrointestinal Distress Nausea, vomiting and diarrhea were reported in workers who drank water, contaminated with nickel sulfate and nickel chloride. 1.14.1.3 Neurological Effects Giddiness and weariness were reported in individuals accidentally exposed to nickel sulphate and nickel chloride (1.63 g Ni/liter) with boric acid in drinking water [62]. 1.14.1.4 Pulmonary Fibrosis In humans and animals, nickel carbonyl causes pulmonary fibrosis. Nickel fumes are respiratory irritants and may also cause pneumonitis. 1.14.1.5 Kidney Damage Kidney damage and frank haematuria were observed [63]. 1.14.2 Subchronic Toxicity (10 100 day) A 6 weeks exposure of nickel fumes (0.07 1.1 mg nickel/m3) in humans caused an increase in air way and eye irritations, headaches and tiredness [64]. 1.14.3 Chronic Toxicity (> 100 days) 1.14.3.1 Dermatitis In sensitized individuals, it is most common effect due to nickel use in jewellery intended for pierced body parts and is often marked by itchy and red skin followed by skin ulceration [65]. 1.14.3.2 Respiratory Disorders Inhalation of nickel dusts and aerosols contributes to respiratory disorders such as asthma [66], pneumoconiosis and can also interfere with kreb ´s cycle. 1.14.3.3 Heart Failure Exposure of nickel tetracarbonyl to levels 50,000 100,000 times greater than levels normally encountered in food or drinking water can cause heart failure and variable degrees of cardiovascular system poisoning [67]. 1.14.3.4 Tumors Nickel powder can induce both epithelial and connective tissue tumors e.g. pelvic, renal cortical and liver tumors when given by subcutaneous, intramuscular or intraperitoneal injection [68]. 1.14.3.5 Kidney Poisoning Nickel in blood is mostly protein bound and accumulates primarily in kidneys resulting in kidney poisoning [69]. 1.14.3.6 Birth Defects Low birth weight infants with sensory abnormalities, such as hearing or sight loss and cardiac malformations are born with nickel exposed mothers [70, 71]. 1.14.3.7 Oxidative Stress Nickel(II) induces oxidative stress in humans [72, 73] by producing either reactive oxygen species, ROS or reactive nitrogen species, RNS. NiCl2 induces lipid peroxidation while ROS generated damage DNA. Nickel binds to DNA repair enzymes and generates oxygen free radicals causing protein degradation [74]. 1.14.3.8 Genotoxicity Ni(CO)4 inhibts DNA dependent RNA synthesis activity by binding to chromatin or DNA and thereby preventing action of RNA polymerase, causing suppresion of messenger RNA dependent induction of enzyme synthesis [75]. 1.14.3.9 Carcinogenicity Nickel subsulphide, nickel oxide, nickel sulphate as well as nickel sulfide fume and dust is believed to be carcinogenic [76, 77]. Independent international scientific bodies have classified mixed sulphidic and oxidic nickel compounds [78] as carcinogens to humans, inclusive of water soluble nickel compounds. There are higher chances of development of lung cancer, nasal cancer, and Prostate cancer in nickel exposed workers [79]. 1.15 Uses of Nickel 1.15.1 Nickel Alloys Nickel in alloyed form has made significant contributions to our present day society. German silver containing 10 30 % nickel is used for ornamental and domestic objects. Monel contains 68% nickel ands is used in apparatus for handling corrosive materials. Invar is important due to very small coefficient of expansion [80]. Nickel is principle alloying element in stainless steel that enhances its heat, corrosion, and stress rupture resistance [81]. Majority of stainless steels contain 8 10 % nickel. Its limitless uses include home and industrial products. 1.15.2 Nickel Electroplating Nickel electroplating is used for both protective and decorative finishes. Nickel chloride, NiCl2, nickel acetate Ni(OCOCH3)2, nickel nitrate, Ni(NO3)2.6H2O and nickel sulphate, NiSO4.7H2O are employed chiefly in nickel electroplating baths [82] while nickel oxide is used as electrolyte. Nickel electroplating changes the chemical, physical and mechanical properties of the workpiece [83]. 1.15.3 Catalytic Hydrogenation Raney nickel is used in a large number of industrial processes because of its stability and high catalytic activity at room temperature. It catalyses hydrogenation of vegetable oils. Soybean oil has been hydrogenated electrocatalytically on raney nickel with 90 100 % efficiencies [84]. Benzene is commonly reduced to cyclohexane using raney nickel for production of nylon. Reduction of Benzene to Cyclohexane Using Raney Nickel Raney nickel is used in reduction of compounds that have multiple bonds. Reduction of Thiophene by Raney Nickel De-Sulfurization of Thioacetals using Raney Nickel 1.15.4 Industrial Applications of Nickel 1.15.4.1 Heavy Industries Nickel based super alloys have high temperature applications in jet engines, gas turbines and rocket engines [85]. Monel can resist corrosion by sea water and is ideal for propeller shaft in boats and desalination plants. 1.15.4.2 Food Chemical processing Industries Monel and stainless steel are used in chemical and food processing industries due to better corrosion resistance at high temperature steam [86]. 1.15.4.3 Ceramics, Paints, Dyes Cosmetic Industries Nickel(II) phthalocyanine, C32H16N8Ni is used as bluish green pigment in the coloring industries [87]. The nickel titanium yellow pigments find great use in polymer and paint applications [88]. Nickel dimethylglyoxime (C8 H14 N4 NiO4) is routinely used as coloring agent in paints, cosmetics and certain kinds of plastics. NiO is used in making glass having ability to absorb visible light but transmits ultraviolet light [89]. In cosmetic products of many brands, the highest level of nickel in eye shadows is about 49 ppm [90]. 1.15.4.4 Textile Rubber Industry Nickel acetate is used as mordant in textile industry. Di-n-butyldithiocarbamate nickel(II) complex, Ni[CS2N(C4H4)2]2 is used as an antioxidant in tires. 1.15.5 Batteries Nickel batteries are dominant in the field of rechargeable electrochemical power sources due to their long cycle life, high power and a reliable performance. Ni(OH)2 is used as positive electrode to significantly boost energy densities in nickel alkaline batteries [91]. Nickel cadmium cells provide 1.2 V and are used in aeroplanes and emergency lighting systems. In industries, these batteries provide high voltage of 250 V with capacities about 5 Ah 100 Ah [92]. Nickel hydrogen (NiH2) battery cells with nickel oxide positive electrode are developed due to high power density and good thermal performance which make them attractive for use in electric vehicles, satellite and space power systems [93]. 1.16 Chemistry of Ligands 1.16.1 Thiourea (Tu) Thiourea, SHYPERLINK http://en.wikipedia.org/wiki/CarbonC(NHYPERLINK http://en.wikipedia.org/wiki/HydrogenH2)2 is lustrous white crystalline compound. It is useful sulfur donor thioamide and planar molecule, soluble in water and polar organic solvents but insoluble in non polar solvents. It has two tautomeric forms but in aqueous solution, thione form predominates. 1.16.2 N,N-Dimethylthiourea (Dmtu) N,N-Dimethylthiourea, C3H8N2S has appearance of colorless to white crystals. It shows coordination through sulfur. Fig. 1.10 Structure of N,N-Dimethylthiourea 1.16.3 1,1,3,3-Tetramethyl-2-thiourea (Tmtu) This substituted thiourea is white crystalline solid. It is sulfur donor ligand. 1.16.4 1,3-Diazinane-2-thione (Diaz) This six membered heterocyclic thione is sulfur donor ligand. 1.16.5 Imidazolidine-2-thione (Imt) It is a sulfur donor five membered heterocyclic thione [94] and has brown crystals. The peculiarity of Imidazolidine-2-thione is presence of a thiouredine fragment. It is planar with non-uniform distribution of à Ã¢â€š ¬ electron density and shows presence of maximum negative charge on exocyclic sulfur. Dipolar form B predominates in resonance hybrid. 1.17 Objective The primary objective of this study is to understand basic chemistry of nickel(II) and its complexes and gain an insight into metal ligand interactions in biological systems with following main objectives. To explore coordination chemistry of nickel(II) with various sulfur donor ligands and develop useful model for biologically active nickel complexes by determining structures of synthesized nickel complexes. Synthesis of nickel(II) complexes with thioamide and thione ligands. Crystallization of as many complexes as possible and determination of their structures by X-ray crystallography. Characterization of complexes by IR and UV-VIS spectroscopy. A comparative study of complexes based on spectroscopic and structural data.

Classroom Management and Diversity Essay

Classroom management and diversity are two very important concepts to consider because classroom management in diverse environments can be a lot different than in less diverse environments. There is so much diversity going on now that everyone should be aware of the importance of classroom management inside the diverse environments. When I talk about diversity in this paper I am referring to ethnic and cultural diversity. There are many different strategies that can help students in more diverse classrooms feel more comfortable and be in a better learning environment. In my paper, I will be touching on five major strategies that help classroom management in more diverse classrooms. These strategies are building trust, engaging personal culture, confronting social dominance and social justice, transforming instructional practices, and engaging the entire school community. I will be talking about all of the advantages to these strategies. Another thing I will be touching on is the importance of classroom management in these diverse classrooms. I will also look at the differences between classroom management in less diverse environments and classroom management in more diverse environments. I will talk about my experiences observing classrooms and the differences between the classroom management strategies each teacher uses. Classroom management is a very critical part of teaching and having good classroom management in a more diverse classroom is a challenging task, but also a very important one. In more diverse environments especially, it is sometimes harder for teachers to have good classroom management. Mainly because the students in more diverse settings tend to act out more or disobey the rules. If students feel like they are in an open and trusting community at school they are more likely to succeed and listen to the teacher’s directions. Building trust, engaging personal culture, confronting social dominance and social justice, transforming instructional practices, and engaging the entire school community is five very important strategies that make classroom management easier. Building trust is one of the most important strategies that help classroom management in more diverse environments. Building trust entails being honest with students and having discussions about race and ethnicity with the entire class. Talking about students different cultures instead of just simply acting like they are not there. One teacher from the Apple Valley School District says, â€Å"I need to move beyond being color-blind. † The main idea of this strategy is to establish positive leaning communities in each classroom. If the students feel like their cultures and ethnicity are accepted they will feel more comfortable. Trust is such an important thing to have in a classroom in order to be able to have good classroom management. If the students feel like they can trust the teacher they will be more open and the teacher will have better control over his or her management (Howard, 2007). The second strategy is engaging in personal culture. This strategy is very important because it can be the difference between high school students dropping out of school or continuing on. The main reasoning of engaging in personal culture is to form authentic and effective relationships across differences. These relationships are very important to students who are going through school. If students feel that their teachers do not care about them they are more likely to drop out of school. Forming relationships with your students is important in order to maintain good classroom management. If the students feel like you enjoy getting to know them and that you respect them then they are more likely to listen and follow directions. If students feel like you do not respect them and could care less about them they are more likely to disobey and possibly even drop out of school all together (Howard, 2007). Confronting social dominance and social justice is the third strategy to better classroom management. This strategy is about making teachers aware of their surroundings and the issues that surround race and class. It forces teachers to think about race and class in a different way and causes them to better understand their students and what their students are going through. During this strategy teachers will come together and have discussions about race, class, gender, immigration, and other forms of diversity. They will open up and get a better consciousness about social dominance and diversity. This will help teachers teach their students better and make them more aware of what is going on around them (Howard, 2007). The fourth strategy is  transforming instructional practices. This strategy is crucial to having good classroom management. The main focus of this strategy is for teachers to shift their teachings to meet the diverse learning needs of students. Also, to use curriculum that honors each student’s culture. For example, if a teacher was working in a school district that was mainly a Spanish speaking area if the teacher had to send something home to the parents they could send one paper home in English and on the back have the same paper written in Spanish. This would make it a lot easier on parents and students of mainly Spanish speaking families. This would also help classroom management because it is very important that your student’s parents understand you (Howard, 2007). The fifth and last strategy is engaging the entire school community. This strategy talks about how if you want to have good classroom management in diverse environments you not only have to involve the students, but also their parents. If the students are not getting any support from their parents it is hard for them to succeed. Teachers can help parents get more involved by sending home news letters and letting them know about any activates going on around the school. Even though this might not always get the students parents involved it still good to try. It is a lot easier to have classroom management when the students feel supported by not only the teacher, but also by their parents (Howard 21). Also students in schools with a strong sense of community are more likely to be academically motivated (Schaps, 2003). I recently observed two different classrooms, one in a diverse environment and one in a less diverse environment. The classroom I observed that was diverse is in the Northeast school district in Reading and the less diverse classroom is in the Pleasant Valley school district in Brodheadsville. The way the teachers in each of these schools manage their classrooms is completely different because of the diversity differences. The biggest difference I came across while observing these two classrooms was how serious each of the teachers has to be. From observing I realized how much harder it is to have good classroom management in more diverse classrooms. For example, in the more diverse classroom the teacher had to be very serious and the teacher in the less diverse classroom joked around a lot. The teacher in the more diverse classroom had to be serious because the students were constantly acting up. The teacher did not have time to joke around because at every moment she had to keep her students on track of what they were supposed to be doing. They constantly needed guidance. When I was observing the less diverse classroom I saw that the teacher joked around a lot. He made funny references and was all around less serious and strict. This was because his students were better behaved. They did act up at certain times, but they were always quick to get back on topic. Another thing that I realized was that the teacher in the diverse environment used all of the strategies that help classroom management and the teacher in the less diverse environment only used two of the strategies. There were a few kids in the less diverse environment that were diverse but the teacher did not recognize them. He did not confront social dominance and justice, transform practices, or engage school community. He just acted as if everyone was the same ethnicity and ignored all differences. Which, is not always the best way to act. When a teacher acts this way even though they are teaching all of the students the same. Sometimes the students that are ethnically different can fall behind or feel as if they are not cared about. Where as the teacher in the diverse environment took advantage of her student’s differences and did all of the strategies, which helped her classroom management become better. By enforcing the strategies the classroom management becomes better because the students respect the teachers more and also usually listen better. The students and teacher benefit from using the five strategies. Keeping control of diverse classrooms is much more challenging than keeping control of less diverse classrooms. There is a big difference between diverse and less diverse classrooms, that is why classroom management is so important. If the teacher in the diverse environment did not use the five strategies I think it would have been very hard for her to have good classroom management in her classroom. The teacher in the less diverse environment however was able to get away with not using the five strategies because his classroom was less diverse so the students were not as hard to handle. Achieving classroom management in diverse classrooms is a very important and challenging task. Classroom management continues to be a serious concern for teachers and especially in urban and diverse learning environments (Milner 2010). Classroom management is so important in order to have a successful running class. It is easier to obtain classroom management in less diverse classrooms but there are five major strategies that help teachers achieve classroom management in diverse classrooms. I mentioned these strategies earlier, they are again building trust, engaging in personal culture, confronting social dominance and social justice, transforming instructional practices, and engaging the entire school community. Without these five strategies it would be almost impossible to gain good classroom management in diverse environments. If a teacher did not use the five strategies it is possible that his or her classroom would not have very good classroom management, depending upon if the classroom was in a diverse environment or not. Like I mentioned earlier in my paper, classrooms in less diverse environments can often get away with not using the five strategies. This is because the students are easier to manage. It is crucial however, for the teachers in the diverse environments to use the strategies. If in the future teachers decided not to use the strategies and instead decided to just ignore the differences between diverse and non-diverse environments it would cause major problems with classroom management. If a classroom had bad classroom management the students would suffer terribly. Some students would not care about their work, some would not listen, and some would just simply drop out. If teachers did not have control over their classrooms the students would not have anyone to listen to or pay attention to. That is why classroom management is so important. There is a way however, to help classrooms in diverse environments have good classroom management and it is to use the five strategies. If teachers in diverse settings continue to use the strategies it will help not only the teachers, by making good classroom management easier to achieve, but it will also help the students because they will learn more if they are listening and paying attention to the teacher. H. Richard Milner IV, B. T. (2010). Classroom management in diverse classrooms. Retrieved from http://uex. sagepub. com. ezaccess. libraries. psu. edu/content/45/5/560. full. pdf html Herbert Elizabeth, A. (1998). Design matters: How school environment affects children. Realizing a Positive School Climate, 56(1), 69-70. Howard Gary, R. (2007). As diversity grows, so must we. Responding to Changing Demographics, 64(6), 16-22. Schaps Eric. (2003). Creating a school community. Creating Caring Schools, 60(6), 31-33.

GMAT and GRE Math - What is 20 of 40 Percent

Are you preparing for the GRE or the GMAT? If these timed graduate and business school exams are in your future, heres a short cut for answering percent questions. More specifically, this article focuses on how to easily calculate the percentage of a number. Suppose a question required you to find 40% of 125. Follow these simple steps. Four Steps to Calculate a Percentage Step 1: Memorize these percents and their corresponding fractions. 100% 150% 1/225% 1/433 1/3% 1/320% 1/510% 1/10 Step 2: Choose a percent from the list that fits with the percent in question. For example, if you are looking for 30% of a number, choose 10% (because 10% * 3 30%). In another example, a question requires you to find 40% of 125. Choose 20% since it is half of 40%. Step 3: Divide the number by the denominator of the fraction. Since youve memorized that 20% is 1/5, divide 125 by 5.125/5 2520% of 125 25 Step 4: Scale to the actual percent. If you double 20%, then youll reach 40%.   Therefore, if you double 25, youll find 40% of 125. 25 * 2 50 40% of 125 50 Answers and Explanations Original Worksheet 1. What is 100% of 63?63/1 632. What is 50% of 1296?1296/2 6483. What is 25% of 192?192/4 484. What is 33 1/3% of 810?810/3 2705. What is 20% of 575?575/5 1156. What is 10% of 740?740/10 747. What is 200% of 63?63/1 6363 * 2 1268. What is 150% of 1296?1296/2 648648 * 3 19449. What is 75% of 192?192/4 4848 * 3 14410. What is 66 2/3% of 810?810/3 270270* 2 54011. What is 40% of 575?575/5 115115 * 2 23012.   What is 60% of 575?575/5 115115 * 3 34513. What is 5% of 740?740/10 7474/2 37

Personal Statement On Emotional Distress - 1601 Words

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