资源简介

(共42张PPT)
Manganese (Mn)
Electron configuration: 4s23d5 4s13d5 3d5 3d4
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 of oxidation states.
Ores:
Pyrolucite: MnO2
Manganite: MnO(OH)
Rhodochrosite: MnCO3
Manganese
pyrolusite: 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. 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.
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Preparation of the element
The most important ore is pyrolusite, manganese(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 manganese(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 hard 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) + 7H2O
Mn(V)
Disproportionation:
3MnO42-(aq) + 4H+(aq) 2MnO4-(aq) + MnO2(s) + 2H2O(l)
Mn(VI) common oxidizing agent
2 MnO4- + 5 SO32- + 6 H+ 2 Mn2+ + 5 SO42- + 3 H2O acidic
2 MnO4- + 3 SO32- + H2O 2 MnO2 + 3 SO42- + 2 OH- neutral
2 MnO4- + SO32- + 2 OH- 2 MnO42- + SO42- + H2O basic
decomposes (explosively on heating)
MANGANESE(VII) OXIDE,
THE MANGANATES(VII)
disproportionates on heating
manganate(VII) ion slowly oxidizes water
in concentrated alkali, manganese(VI) is more stable than manganese(VII)
in neutral or acid solution manganese(VI) disproportionates
MANGANESE(IV) OXIDE, MnO2
neutral
acidic
Lead (IV) oxide and concentrated nitric acid
Iron (Fe)
Electron configuration: 4s23d6 4s13d6 3d6 3d5
Ores:
Hematite: Fe2O3 (impure)
Limonite: FeO(OH).nH2O
Magnitite: Fe3O4
Siderite: FeCO3
Properties
Very abundant
Main oxidation states: II, III
Can be magnetized.
Uses
Not 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.
Preparation of the Element
In 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 (concentrated) solution, which is strongly acidic.
FeCl3.6H2O yellow [FeCl2(H2O)4]Cl·2H2O
Coordination Compounds
[Fe(CN)6]3-, [Fe(CN)6]4-,
[Fe(SCN)(H2O)5]2+;
[Fe(H2O)6]2+; green
[Fe(H2O)6]3+; purple
Coordination Compounds II
Fe3+ ions and [Fe(CN)6]4- gets blue precipitate, prussian blue;
Fe2+ ions and [Fe(CN)6]3- gets blue precipitate, Turnbull’s blue.
KFe[Fe(CN)6]
test 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)5NO]2+ which appears as a "brown ring' at the acid-aqueous interface
Iron is the fourth most abundant element in the earth's 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.
Iron
Ferrocene: a sandwich compound
Chemistry of Ferrocene
Metallocenes undergo reactions similar to those of simple aromatic hydrocarbons.
Possible structures of [Fe( 5-C5H5)2]
Cobalt (Co)
Electron configuration: 4s23d7 3d8 3d7 3d6
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 electroplating 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
Cobalt 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, CoF3, is obtained.
[Co(H2O)6]2+, pink
simple cobalt(III) cation cannot exist in aqueous solution (which it would oxidize to oxygen).
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 yellow product had the formula CoCl3. 6NH3
Alfred Werner was awarded the
Nobel Prize for chemistry in 1913)
@1890 ~1913
Founding of Coordination Chemistry
charcoal is a catalyst
If hydrogen peroxide is used as the oxidant, a red aquopentamminocobalt (III) chloride, [Co(NH3)5H2O]Cl3, is formed
treatment with concentrated hydrochloric acid gives the red chloropentamminocobalt(III) chloride, [Co(NH3)5Cl]Cl2
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 oxidized in alkaline conditions
or when a cobalt(III) is decomposed by aqueous alkali.
On heating it gives the black mixed oxide Co3O4. [ CoO· Co2O3 ]
Chemistry of Cobalt (II)
The precipitate
is often blue, but becomes pink on standing; it dissolves in excess
alkali to give the blue [Co(OH)4]2- ion, and in slightly alkaline
solution is easily oxidized by air to a brown solid of composition
CoIIIO(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 decompose the nitrite)
Na salt is very soluble, but K+,Rb+,Cs+,NH4+ salt are very insoluble in H2O
CoCl2
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 COBALT
For a cobalt(II) salt the precipitation of the blue pink 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 ethanoic acid gives a precipitate of the potassium hexanitro-cobaltate(III), K3[Co(NO2)6]
Decomposition 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: 4s23d8 3d9 3d8 3d7
Nickel occurs more abundantly than cobalt.
Properties
Hard, malleable and ductile, silvery-white, capable of taking on a high polish.
Main oxidation state: II
Soluble in all acids except concentrated nitric acid.
Nickel carbonyl is very toxic.
Uses:
Used extensively in alloys: stainless steel, coinage metals.
The Nickel is 25% nickel and 75% copper
Electroplated Ni gives a protective coat for other metals.
Rechargeable batteries (Ni-Mh, NiCd)
Preparation of the element
The metal obtained by reduction can be purified by the Mond process, in which it is heated to 320 K with carbon monoxide to give the pure, volatile tetracarbonyl Ni(CO)4; the latter when heated to 500 K gives the pure metal and carbon monoxide is recovered
[Ni(H2O)6]2+, green
Ni(OH)2, green
NiO, black
Fe2+
H+
Fe(OH)2
NH3 · H2O
Fe2+ 淡绿
OH-
Fe(OH)2(s,白)
O2
Fe(OH)3(s,红棕)
HCl
Fe3+
Co(NH3)63+红
O2
Co(NH3)62+黄
NH3·H2O
Co(OH)Cl(s,蓝)
NH3· H2O
Co2+(Cl-) 粉红
OH-
Co(OH)2(s,粉红)
NaClO
Co(OH)3(s,红棕)
浓HCl
Co2+（CoCl4,蓝）
Ni(NH3)62+蓝
NH3 · H2O
Ni2(OH)2SO4浅绿
NH3 · H2O
Ni2+(SO42-) 淡绿
OH-
Ni(OH)2(s,果绿)
NaClO
NiO(OH)(s,黑)
浓HCl
Ni2+
鉴定：Fe(NCS)n3-n 血红 Co(NCS)42- 天蓝 Ni(DMG)2(s,鲜红)
[KFe(CN)6Fe]x(s,蓝) （丙酮）
2-

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