化学专业英语《Chemistry English》课程教学资源（PPT课件）Lecture 09

RegulationsforAmericanPupilsandMiddle SchoolStudentsAlways referto ateacher by titleand last nameGettoclassontimeRaise your hand when you want to ask a questionYou mayspeak to theteacherfromyour desk whileyou areseatedWhen you are absent, you must make up the workyouhavemissed.Askeithertheteacherora classmateforthe workIfyou expecttobeawayfromschool becauseofanemergency,tellyourteacherinadvanceandaskforthe work you will missAll assignmentsyou handinmustbeyour ownworkNever cheat on a test

1 Regulations for American Pupils and Middle School Students • Always refer to a teacher by title and last name • Get to class on time • Raise your hand when you want to ask a question • You may speak to the teacher from your desk while you are seated • When you are absent, you must make up the work you have missed. Ask either the teacher or a classmate for the work • If you expect to be away from school because of an emergency, tell your teacher in advance and ask for the work you will miss • All assignments you hand in must be your own work • Never cheat on a test •

Transition elements:thefactsITransition elements: the facts IDEFINITIONSd block element: any element with its highestenergy electron in a d orbitalTransition element: those elements havingions with electrons in an incomplete d shelli.e. from titanium to copperSc3+: [Ar] 3d04s0NodelectronsZn2+:[Ar] 3d10..not transitionalfulldshellsd-block..nottransitionaltransitionelementsCu2+:[Ar]3d9incompletedshellsvTiCrCoNiMnFeCu..transitional2

2 Transition elements: the facts I DEFINITIONS d block element: any element with its highest energy electron in a d orbital Transition element: those elements having ions with electrons in an incomplete d shell i.e. from titanium to copper Transition elements: the facts I

Transition elements: the facts ITYPICALPHYSICALPROPERTES:all metalshigh m.p. chromium 2160K, iron 1800K compared with sodium 371Kharddensebut not titaniumsimilar atomic and ionic sizes and ionization energiesUnlike elements in the s and p blocks, there is little change inatomic and ionic radii as the d block is crossed. This is because theadditional electrons are going into an inner d sub-shell. This alsoresults in only a small increase in ionization energy across the dblock. Although each successive nucleus has one more proton, thisextra positive charge is partly shielded from the outer 4s electronsby the extra d electron in an underlying shell.3

3 Transition elements: the facts I TYPICAL PHYSICAL PROPERTIES: all metals high m.p. chromium 2160K, iron 1800K compared with sodium 371K hard dense but not titanium similar atomic and ionic sizes and ionization energies. Unlike elements in the s and p blocks, there is little change in atomic and ionic radii as the d block is crossed. This is because the additional electrons are going into an inner d sub-shell. This also results in only a small increase in ionization energy across the d block. Although each successive nucleus has one more proton, this extra positive charge is partly shielded from the outer 4s electrons by the extra d electron in an underlying shell

Transition elements:thefactsITYPICALCHEMCALPROPERTIES1.Variable valencyTransition elements show many oxidation states, these fall into twokinds:higher oxidation states:thecovalently bonded oxo-compoundse.g. CrO4?-; Cr,O,2-; MnO4; MnO42-lower oxidation states:theatomicionse.g. Cr3+; Cr2+; Mn3+; Fe3+; Fe2+; Cu?+; Cu*4

4 Transition elements: the facts I 1. Variable valency Transition elements show many oxidation states; these fall into two kinds: ● higher oxidation states: the covalently bonded oxo-compounds e.g. CrO4 2- ; Cr2O7 2- ; MnO4 - ; MnO4 2- ● lower oxidation states: the atomic ions e.g. Cr3+ ; Cr2+ ; Mn3+ ; Fe3+ ; Fe2+ ; Cu2+ ; Cu+ TYPICAL CHEMICAL PROPERTIES

Transition elements: the facts I2. Colored compoundsMany of the compounds of the transition elements are coloredcommonexamples:CrO.2--yellow,Cr3+-green,Cr2+-blue;Cr20,2-orange;chromate(VI)dichromateMnO.?--green;MnO4-purple;Mn?+-pale pink(per)manganate(VII)manganate (VI)Fe3+-yellow; Fe2+-greenCo2+-pink in water, blue when dryCu?+-blue5

5 Transition elements: the facts I 2. Colored compounds Many of the compounds of the transition elements are colored. ● common examples: CrO4 2- -yellow; Cr2O7 2- -orange; Cr3+ -green; Cr2+ -blue; chromate(VI) dichromate MnO4 - -purple; MnO4 2- -green; Mn2+ -pale pink (per)manganate(VII) manganate (VI) Fe3+ -yellow; Fe2+ -green Co2+ -pink in water, blue when dry Cu2+ -blue

Transition elements: the facts I3.Catalytic propertiesTransition metals and their compounds can beheterogeneous catalysts, forexample:iron in the Haber processV,O, in the Contact processhomogeneous catalysts, forexample:Mn?+ in the reaction between ethanedioate and manganate(VII)Fe2+/Fe3+ in the reaction between iodide ions andperoxydisulphate (VI)6

6 Transition elements: the facts I 3. Catalytic properties Transition metals and their compounds can be: ● heterogeneous catalysts, for example: iron in the Haber process V2O5 in the Contact process ● homogeneous catalysts, for example: Mn2+ in the reaction between ethanedioate and manganate(VII) Fe2+ /Fe3+ in the reaction between iodide ions and peroxydisulphate (VI)

Transition elements: the facts IlTransition elements: the facts IlMagneticpropertiesSome of the transition elements are ferromagnetic which meansthat they can be magnetized, e.g. iron, cobalt, and nickel.Some of their compounds are paramagnetic which means thatthey move in a strong magnetic field.7

7 Transition elements: the facts II Magnetic properties Some of the transition elements are ferromagnetic which means that they can be magnetized, e.g. iron, cobalt, and nickel. Some of their compounds are paramagnetic which means that they move in a strong magnetic field. Transition elements: the facts II

Transitionelements:thefactsIlTYPICAL CHEMICALPROPERTIES4. Complex ion formationA complex ion consists of a central ion or atom surrounded byother particles called ligands. A ligand is a particle (ion ormolecule) with a lone pair which forms a dative covalent bond tothe central particle. The ligands are said to be coordinated to thecentral particle.NOOCCNligandsCNNCOFestdativebondformingNCOCONTransition metal ions form many complex ions which vary incharge, shape, color, and stability8

8 Transition elements: the facts II 4. Complex ion formation A complex ion consists of a central ion or atom surrounded by other particles called ligands. A ligand is a particle (ion or molecule) with a lone pair which forms a dative covalent bond to the central particle. The ligands are said to be coordinated to the central particle. TYPICAL CHEMICAL PROPERTIES Transition metal ions form many complex ions which vary in charge, shape, color, and stability

Transition elements: the facts IlShapeLigands differ in size and this means that the number which can fitaround the central cation changes. Ammonia and water arerelatively small ligands and six of each can fit around a cobalt orcopper ion forming octahedral complexes, while only four of thelarger chloride ion can fit around either the cobalt or copper ionsoctahedral2+2+H20NH3SilverisunusualinformingH20NH3linearcomplexes.NH3NH3-CU--Co-H20-H20[NC—Ag - CN]NH3H20H20NH3tetrahedral2-[H,N—Ag -NH,]2-CICI/1[O,S2Ag - S,O3]3CoCuCICICICICICI9

9 Transition elements: the facts II Shape Ligands differ in size and this means that the number which can fit around the central cation changes. Ammonia and water are relatively small ligands and six of each can fit around a cobalt or copper ion forming octahedral complexes, while only four of the larger chloride ion can fit around either the cobalt or copper ions. Silver is unusual in forming linear complexes. [NC—Ag – CN]- [H3N—Ag –NH3 ] + [O3 S2—Ag – S2O3 ] 3-

Transition elements:thefactsIlChargeThe charge of the complex depends on the relative charges of thecentral ion or atom and the ligands, and on the number of ligandsaround it. Complex ions may be cations or anionscationiccomplexesanioniccomplexesCuC1 2-(aq),Cu(NH,)4(H,O),2+(aq)FeCNS2+(aq)Fe(CN)3-(aq)ColorThe color of the complexes is affected by the nature of the ligandand the number of ligands around the central cation.10

10 Transition elements: the facts II Charge The charge of the complex depends on the relative charges of the central ion or atom and the ligands, and on the number of ligands around it. Complex ions may be cations or anions Color The color of the complexes is affected by the nature of the ligand and the number of ligands around the central cation. anionic complexes CuCl4 2- (aq), Fe(CN)6 3- (aq) cationic complexes Cu(NH3 ) 4 (H2O)2 2+(aq), FeCNS2+(aq)