无机化学课件26mniron group

1、Manganese (Mn) Electron configuration: 4s23d54s13d53d53d4 Properties Hard, brittle, lustrous silver-blue. Uses Added to steels to increase resistance to shock and wear. Manganese (IV) oxide is used in dry cell batteries. KMnO4 - Strong oxidizer. Essential to all living things. Has a very wide range

2、of oxidation states. Ores: Pyrolucite: MnO2 Manganite: MnO(OH) Rhodochrosite: MnCO3Manganesepyrolusite: MnO2 软锰矿All steels contain some Mn to prevent brittleness. Higher percentage of Mn will enhance hardness of the steel.Important compounds: KMnO4(purple), Mn2+(light pink).MnO2: dry cell industry.

3、From high quality ore or made electrolytically from MnSO4 solution. Glass decolorizer: presence of Fe(II)greenish color, add MnO2 to molten glass produces red-brown Mn(III), equalizes absorption! Selenium has similar properties. Preparation of the element The most important ore is pyrolusite, mangan

4、ese(IV) oxide. Reduction of this ore by heating with aluminium gives an explosive reaction, and the oxide Mn3O4 must be used to obtain the metal. The latter is purified by distillation in vacuo just above its melting point (1517 K); the pure metal can also be obtained by electrolysis of aqueous mang

5、anese(II) sulphate.Property of the Metal The metal looks like iron; stable over various temperature ranges. Although not easily attacked by air, it is slowly attacked by water dissolves readily in dilute acids to give manganese (II) salts. The stable form of the metal at ordinary temperatures is har

6、d and brittle hence manganese is only of value in alloys, for example in steels (ferroalloys) and with aluminum, copper and nickel.Mn2+2 Mn2+(aq) + 5 NaBiO3(s) + 14 H+(aq) 2MnO4-(aq) + 5 Bi3+(aq) + 5 Na+(aq) + 7H2OMn(V)Disproportionation:3MnO42-(aq) + 4H+(aq) 2MnO4-(aq) + MnO2(s) + 2H2O(l)Mn(VI)comm

7、on oxidizing agent2 MnO4- + 5 SO32- + 6 H+ 2 Mn2+ + 5 SO42- + 3 H2Oacidic2 MnO4- + 3 SO32- + H2O 2 MnO2 + 3 SO42- + 2 OH- neutral2 MnO4- + SO32- + 2 OH- 2 MnO42- + SO42- + H2Obasic poses (explosively on heating)MANGANESE(VII) OXIDE,THE MANGANATES(VII)disproportionates on heatingmanganate(VII) ion sl

8、owly oxidizes waterin concentrated alkali, manganese(VI) is more stable than manganese(VII)in neutral or acid solution manganese(VI) disproportionatesMANGANESE(IV) OXIDE, MnO2neutralacidicLead (IV) oxide and concentrated nitric acidIron (Fe)Electron configuration: 4s23d64s13d63d63d5Ores:Hematite: Fe

9、2O3 (impure)Limonite: FeO(OH).nH2OMagnitite: Fe3O4Siderite: FeCO3PropertiesVery abundantMain oxidation states: II, IIICan be magnetized.UsesNot very useful in “pure” form, used to make steel by mixing with a small amount of carbon.Iron oxides are used as pigments.Has immense biological importance.Pr

10、eparation of the ElementIn dilute nitric acid:FeCl3 When the anhydrous solid is heated, it vaporizes to form first Fe2Cl6 molecules, then the monomer FeCl3 and finally FeCl2 and chlorine. It fumes in air (with hydrolysis) and dissolves readily in water to give a yellow (dilute) or brown (concentrate

11、d) solution, which is strongly acidic. FeCl3.6H2O yellow FeCl2(H2O)4Cl2H2OCoordination Compounds Fe(CN)63-, Fe(CN)64-, Fe(SCN)(H2O)52+; Fe(H2O)62+; green Fe(H2O)63+; purpleCoordination Compounds II Fe3+ ions and Fe(CN)64- gets blue precipitate, prussian blue; Fe2+ ions and Fe(CN)63- gets blue precip

12、itate, Turnbulls blue. KFeFe(CN)6test for a nitrate When concentrated sulfuric acid is added to a nitrate in the presence of aqueous iron(II) sulfate, the nitrogen oxide liberated forms a brown complex Fe(H2O)5NO2+ which appears as a brown ring at the acid-aqueous interface Iron is the fourth most a

13、bundant element in the earths crust. Iron is obtained from the ores hematite (Fe2O3) and magnetite (Fe3O4) by reduction with coke. The adult human body contains about 4 grams of iron, mostly in the form of hemoglobin. IronFerrocene: a sandwich compound Chemistry of Ferrocene Metallocenes undergo rea

14、ctions similar to those of simple aromatic hydrocarbons. Possible structures of Fe(5-C5H5)2Cobalt (Co) Electron configuration: 4s23d73d83d73d6 Properties Hard, brittle, lustrous blue-white. Main oxidation state: II Ores: Cobaltite CoAsS Uses Used as an alloy in magnets, jet engine parts. Used in ele

15、ctroplating because of its attractive appearance, hardness and resistance to oxidation. Vitamin B12 is a cobalt complex. Cobalt salts have been used for centuries to produce brilliant blue colors in porcelain, glass, pottery and enamels. The artificial isotope 60Co is used as a tracer.The element Co

16、balt is a bluish silvery metal, exhibits ferromagnetism. Chemically it is somewhat similar to iron; when heated in air it gives the oxides Co3O4 and CoO but it is less readily attacked by dilute acids. With halogens, the cobalt(II) halides are formed, except that with fluorine the (III) fluoride, Co

17、F3, is obtained. Co(H2O)62+, pink simple cobalt(III) cation cannot exist in aqueous solution (which it would oxidize to oxygen).Co(II)Co(III) Observation: ammoniacal solution of a cobalt(II) salt changed color on exposure to air. 1798 if cobalt(II) chloride was oxidized in presence of ammonia, the y

18、ellow product had the formula CoCl3. 6NH3Alfred Werner was awarded theNobel Prize for chemistry in 1913)1890 1913Founding of Coordination Chemistry charcoal is a catalyst If hydrogen peroxide is used as the oxidant, a red aquopentamminocobalt (III) chloride, Co(NH3)5H2OCl3, is formed treatment with

19、concentrated hydrochloric acid gives the red chloropentamminocobalt(III) chloride, Co(NH3)5ClCl2 Low spin Co(III) compounds are very kinetically inert. We can even separate optical isomers!Cobalt(III) oxide Cobalt(III) oxide is obtained as a brown precipitate Co2O3.aq when cobalt(II) hydroxide is ox

20、idized in alkaline conditions or when a cobalt(III) is posed by aqueous alkali. On heating it gives the black mixed oxide Co3O4. CoO Co2O3 Chemistry of Cobalt (II)The precipitateis often blue, but es pink on standing; it dissolves in excessalkali to give the blue Co(OH)42- ion, and in slightly alkal

21、inesolution is easily oxidized by air to a brown solid of compositionCoIIIO(OH).With sodium hydroxide solution and hydrogen peroxide etc.excess sodium nitrite is added to a cobalt(II)salt in presence of ethanoic acid (a strong acid would pose the nitrite)Na salt is very soluble, but K+,Rb+,Cs+,NH4+

22、salt are very insoluble in H2OCoCl2 Anhydrous cobalt(II) chloride is blue, and the solid contains octahedrally-coordinated cobalt the hydrated salt CoCl2. 6H2O is pink, with each cobalt surrounded by four water molecules and two chloride ions in a distorted octahedron.TESTS FOR COBALTFor a cobalt(II

23、) salt the precipitation of the bluepink cobalt(II) hydroxide by alkali, or precipitation of black cobalt(II) sulfide by hydrogen sulphide provide useful tests; the hydroxide is soluble in excess alkali and is oxidized by air to the brown CoO(OH).Addition of excess potassium nitrite acidified with e

24、thanoic acid gives a precipitate of the potassium hexanitro-cobaltate(III), K3Co(NO2)6 position of most cobalt(III) complexes by boiling with alkali gives a brown precipitate of the hydrated oxide Co2O3 .aq. This compound will quantitatively oxidize iodide to iodine.Nickel (Ni)Electron Configuration

25、: 4s23d83d93d83d7Nickel occurs more abundantly than cobalt.PropertiesHard, malleable and ductile, silvery-white, capable of taking on a high polish.Main oxidation state: IISoluble in all acids except concentrated nitric acid.Nickel carbonyl is very toxic.Uses:Used extensively in alloys: stainless steel, coinage