'Periodic Properties Essay\r'

'The halogens F, Cl, Br and I (At has not been include because of its scarcity and nuclear instability) be very unstable non-metals that occur in the penultimate base of the episodic table, hence they al angiotensin converting enzyme require just superstar electron to complete their valence shell.\r\nAll of the elements exists as diatomic break peecules (F2, Cl2, Br2, I2) in which the atoms argon joined by single covalent bonds. Going overmaster a group of the periodic table, for successive elements there are more energy levels filled with electrons, so the outside electors are in higher energy levels and far from the core group. Fluorine and centiliter are gases, bromine a liquid and ace a immobile that forms a violet vapour on heating. The halogens are all quite electronegative elements. They require just one electron to complete their valence shell, hence they right away gain electrons to form the singly charged halide ions (F�,Cl�,Brï¿à ‚½,I�). The eternal sleep with which they gain electrons gained is further from the nucleus and hence dinky wellly attracted. This means that, in contrast to the foot metals, the reactivity of the halogens decreases expiry down the group.\r\nMethod\r\n1) try out the solvability of Iodine:\r\n1. A very niggling amount of one was rear into water, cyclohexane and KI(aq) respective(prenominal)ly\r\n2. The excuseing dislodges of the sources and the solubility in each closure were preserve\r\n2) demonstrate iodine reacts with amylum:\r\n1. Three drops of I2-KI source were vomit up into a test tube\r\n2. A few drops of amylum resultant were added after that\r\n3. The coloration of firmness was put down\r\n3) hear the acid-base properties:\r\n1. A few drops of chlorine water were put in a test surface, and it was tested with universal indicator musical theme\r\n2. This was tell commencement ceremony using water and and then using iodine source so rt of of the chlorine water\r\n3. The color changes were preserve\r\n4) Displacements amidst halogen elements:\r\n1. 2cm prudence of each aqueous solution: sodium chloride, yard bromide and potassium iodide were put into 3 respective test tubes and labeled\r\n2. An equal volume of chlorine water was added into each test tube and the results were recorded\r\n3. A little hexane was added to form a shed light on fastness layer of a non- diametral solvent\r\n4. The mixtures were shake and the changes were recorded\r\n5. measuring 1, 2, 3 and 4 were repeated first using water and then iodine solution instead of chlorine water\r\n5) Tests for halide ions [Halide ions (Cl-, Br- and I-) with atomic number 47 ions]:\r\n1. About 1cm depth of aqueous sodium chloride was put into a test tube\r\n2. A little aqueous silver nitrate was added and then the observations were recorded\r\n3. The test tube was place in a sunny place, and left there for about 5 legal proceeding and then it wa s observed again\r\n4. Step 1, 2 and 3 were repeated using aqueous potassium bromide, then aqueous potassium iodide instead of sodium chloride\r\n?Data Collection?\r\n1) The solubility of iodine in different solvent\r\nColor\r\nsolvability\r\nWater\r\nColor little\r\nInsoluble\r\nCyclohexane\r\nPurple\r\n fat-soluble\r\nEthanol\r\nYellow\r\n dissoluble\r\nKI(aq)\r\nYellow-brown\r\nSoluble\r\n2) Test iodine reacts with starch:\r\nThe color of the solution is dispirited.\r\n3) Test the acid-base properties:\r\nCl2\r\nBr2\r\nI2-KI\r\npH value\r\n4\r\n3\r\n12\r\n4) Displacements among halogen elements:\r\nThe color change of the solution after Cl2, Br2, I2 added into NaCl, KBr and KI respectively\r\nCl2\r\nBr2\r\nI2\r\nNaCl\r\nNo change\r\nNo change\r\nBrown\r\nKBr\r\nPale icteric solution\r\nNo change\r\nBrown\r\nKI\r\nyellow\r\nyellow\r\nBrown\r\nThe color of the upper layers of the solution after hexane added\r\nCl2\r\nBr2\r\nI2\r\nNaCl\r\nNo change\r\nNo change\r\nPurple cherry\ r\nKBr\r\nPale purple\r\nNo change\r\nPurple red\r\nKI\r\npurple\r\nPale purple\r\nPurple red\r\n5) Tests for halide ions:\r\nHalide ions (Cl-, Br- and I-) with silver ions:\r\nNaCl\r\nWhite precipitate is produced\r\nDarkens after it was placed in sunlight\r\nKBr\r\nCream precipitate is produced.\r\nKI\r\nYellow precipitate is produced.\r\n?Data Analysis?\r\n1) The solubility of iodine in different solvents:\r\nThe solubility is big in non-polar solvent (water, ethanol) and smaller in polar solvents.(cylohexane and KI) The purple color of iodine in cyclohexane is that because in non-polar solvents, iodine froms the violet solution.\r\n2) Test iodine reacts with starch:\r\nAccording to the general knowledge we knew, the phenomenon of this reaction should be blue, but the color observed was black-green. That was because some of the starch hydrolysis in water and produced something could make the color darker.\r\n3) Test the acid-base properties:\r\n1. Cl2:\r\nThe color of the univer sal indicator papers showed that Cl2 is tender acid.\r\n2. Br2:\r\nThe color of the universal indicator papers showed that Br2 is a kind of acid, but not very strong.\r\n3. I2:\r\nThe color of the universal indicator papers showed that I2 is a strong base. Actually, I2 is acid. The footing is that the true color of I2 is red-brown, that made us lowlife’t see the phenomenon clearly.\r\n4) Displacements mingled with halogen elements:\r\nAs what I mentioned above in background, the rule of burnments between halogen elements is that more unstable ones displace less reactive ones.\r\nThat’s the creator wherefore Br -can’t displace Cl -, and I -can’t displace Br †and Cl-. When there was no reaction between two elements, the color we observed was the blend of original colors of the less reactive element and the solution engageing the more reactive element. If there’s a reaction between two elements, the color we can observe is the color of the displaced element.\r\nAccording to the information we got from Internet, we knew hexane is a kind of oil and is insoluble in water-solvent. That was the reason why we could differentiate the two layers of each solution very clearly.\r\nThe colors of each solution’s under layer were the original colors of the salty solutions. There were two kinds of instances of the color of upper layer of each solution. For the solutions those do not have I †ion, they were colorless. That’s because hexane is colorless and cannot react with Cl †or Br -. Another instance is that the solutions include I -, when I †meets hexane, it testament show the color of itself. That was why we could observe color of purple in this experiment.\r\n5) Test for halide ions:\r\nWhen halide ions dissolved into silver salts, then the precipitate is come along commonly.\r\nThe white precipitate is AgCl: AgNO3+NaCl�AgCl+NaNO3\r\nThe off-white precipitate is AgBr: AgNO3+KBrï ¿½AgBr+NaNO3\r\nThe ghastly yellow precipitate is AgI: AgNO3+NaI�AgI+NaNO3\r\nAfter 10 minutes under the sunshine, photodissociation happened on all of them, so the black precipitate on the bottoms of three test tubes are the products of photodissociation.\r\n1. Going down the group, the elements of this group have the resembling effective nuclear charge. Atomic radius of these elements becomes bigger because of the increase of the number of energy levels. The attraction between nucleus and valence electrons gets weaker. Less energy is requisite to remove the first electron from one mole of gaseous atoms. The ionization energy going down the group decreases. The ability to attract electrons becomes weaker. The electronegativity going down the group decreases.\r\n2. Organic solvents always reserve the element carbon. In organic fertilizer solvents don’t contain the element carbon. The most common solvent, water, is an example of an inorganic solvent. There are many more organic solvents than inorganic solvents. Compare with organic and inorganic solvent, the solubility of iodine is higher in organic solvent.\r\n3. The oxidizing office staff of the halogens decrease going down the group as the size of the atoms increase going down the group as the size of the atoms increases and the attraction between the nucleus and the electrons becomes less. In that case, going down the group, the elements become less powerful oxidising agents. This means that a higher halogen pass on displace a turn down halogen from its salts. A lower halogen cannot displace a higher halogen from its salts.\r\n4. When starch reacts with iodine, the classifiable blue black color result appear. That’s a good way for us to mention starch and iodine.\r\n5. After photodissociation, the color of some precipitates will change. will become black. That’s the most diaphanous one. Other precipitates will become darken.\r\n1. Because we use solid iodine in the first experiment. If we add the solvent into the test tube first, the test tube will be wet and the solid iodine we put in later will attach on the surface inside instead of fall into the liquid. For this reason we must add solid iodine first in experiment 1.\r\n2. According to the first experiment, we free-base that the solubility of iodine in pure water is very low. But the solubility of iodine in potassium iodide solution is relatively much higher. So we use I2-KI solution to increase the amount of iodine in order to let the phenomenon more obvious.\r\n speech\r\n1) �Chemistry�(for use with the International Baccalaureate sheepskin Programme)\r\n[3rd Edition] <John Green & Sadru Damji>\r\nFirst create in 2007 by IBID Press, Victoria, Page 77 to 78.\r\n2) http://www.epa.gov/ttn/atw/hlthef/hexane.html\r\n3) http://baike.baidu.com/ imagine/373611.htm\r\n4) http://baike.baidu.com/view/908645.htm\r\n'