The transition elements (d block) and inner transition e.ppt

The transition elements(d block)and inner transition elements(f block)in the periodic table.,Transition Metal ChemistryOne striking characteristic of the representative elements was that their chemistry changes markedly across a given period as the number of valence electrons changes.The chemical similarities occur mainly within the vertical groups.In contrast,the transition metals show great similarities within a given period as well as within a given vertical group.Why?,Transistion Metals Chemistry&Electron ConfigurationThis difference occurs because the last electrons added to the transition metal elements are inner electrons:d electrons for the d-block transition metals and f electrons for the lanthanides and actinides.These inner d and f electrons cannot participate in bonding as readily as the valence s and p electrons.Thus,the chemistry of transition elements is not as greatly affected by the gradual change in the number of electrons as is the chemistry of the representative elements.Also note that the transition metals do not extend all the way across the d-block because the Group 12 elements(zinc,cadmium,and mercury)are not normally considered to be transition elements.Because their d-orbitals are full,the Group 12 elements have properties that are more like those of main-group metals than transition metals.,SOLUTION:,Electron Configurationsof Transition Metal Atoms&Ions,(a)Zr is the second element in the 4d series:Kr5s24d2.,(b)V is the thired element in the 3d series:Ar4s23d3.In forming V3+,three electrons are lost(two 4s and one 3d),so V3+is a d2 ion:Ar3d10.,(c)Mo lies below Cr in Group 6B(6),so we expect the same except in configuration as for Cr.Thus,Mo is Kr5s14d5.In forming the ion,Mo loses the one 5s and two of the 4d electrons to become a 4d3 ion:Kr4d3.,Transition Metals&Electron ConfigurationWrite the electron configuration for the following transition metals/ions:A.CrB.PtC.Tc+4D.Ir+E.Ru+4F.Mo+2G.Co+3,Transition Metal ChemistrySo what charateristics can we expect with transition elements?(1)Variable oxidation states except for the first&last column.The central group having the most variety.(2)All the d-block elements are metals.Most of these“d-metals”are good electrical conductors,malleable,ductile,and lustrous.Generally,their melting and boiling points are higher than those of the main-group elements.They are“hard”metals except for Zn.(3)The low oxidation state ions are generally good reducing agents(they undergo oxidation)and all 3d elements reduce H+except Cu.Recall the activity series.M Mn+ne-,The Period 4 transition metals.,Transition Metal Chemistry(4)The atomic radii of the second row of d-metals are typically greater than those in the first row.The atomic radii in the third series(Period 6),however,are about the same as those in the second row and smaller than expected.This effect is due to the lanthanide contraction,which is the decrease in radius along the first row of the f-block.This decrease is due to the increasing nuclear charge along the period coupled with the poor shielding ability of the f-electrons.When the d-block resumes(at lutetium),the atomic radius has fallen from 224 pm for barium to 172 pm for lutetium.3d 4d 5d,Horizontal trends in key atomic properties of the Period 4 elements.,Transition Metal Chemistry(5)PeriodicityThe atomic radius decreases across a period reaching a constant size due to shielding by the other electrons.Electronegativity generally increases across a period slightly.Ionization energy gradually increases across a period.Atomic size and oxidation state has a major effect on the nature of bonding.Ionic bonding is more prevalent for lower oxidation state ions and covalent bonding is preferred for the higher states.,Vertical trends in key properties within the transition elements.,General Properties of Transition Metal IonsSc scandium:rare on earth,found in electronic devices Sc3+Ti titanium:0.6%by mass on earth,low density,high strength,TiO2 is an opaque material used as a pigment,Ti(H2O)63+is a purple solution.V vanadium:0.025 by mass,used in alloys&as a catalyst V2O5VO2+(+5)yellow VO2+(+4)blue V3+(+3)blue-greenV2+(+2)violetCr chromium:hard,brittle,lustrous,forms an invisible oxide coating,many colored compounds,most common oxid states+2,+3,&+6Cr2+-chromous:bright blue,powerful reducing agentCr3+-Cr2O3 dark green solid that dissolves in water Cr(H2O)6+2Cr6+-chromic:oxidizing agent,CrO42-&Cr2O72-Mn manganese:0.1%by mass,used to produce hard steel,Mn(H2O)62+is light pink,and MnO4-is deep purple(a strong oxidizing agent).Fe iron:4.7%by mass,white lusterous,fairly soft,and highly reactive.Fe(H2O)63+is a yellow solution that is quite acidic.,General Properties of Transition Metal IonsCo cobalt:relatively rare,hard,bluish-white metal used to make alloys.Co(H2O)62+is rose colored.Ni nickel:abundant,silver-white metal with high electrical Cu(H2O)6+is greenZn zinc:colorless solutions,white lustrous,active metal,main ore is sphalerite(ZnFe)S,reducing agent,tarnishes rapidly,90%is used to galvanize steel,Zn2+,Transition Metal Chemistry(in depth)In forming ionic compounds with nonmetals,the transition metals exhibit several typical characteristics:1.Various oxidation states can be found depending on the placement of the transition metals.Elements at the ends of each row occur in only one oxidation state other than zero(exception:mercury).Most other elements have at least two oxidation states other than zero,and elements closer to the center of each row have the widest range of oxidation states.Furthermore,elements in the second and third rows are most likely to reach higher oxidation states than those in the first row.,Transition Metal Chemistry(in depth)2.An element with a high oxidation is likely to be a good oxidizing agent.Compounds that contain the transition metal element in a low oxidation state are often good reducing agents.3.Cations are often complex ions,species in which the transition metal ion is surrounded by a certain number of ligands(molecules or ions that behave as Lewis bases).These complexes have three major components:a central metal atom,ligands,and counter ions.Identify each component in the following complexes:K4Fe(CN)6Co(NH3)6Br3 We will study these in more detail later.,Orbital Occupancy,*Most common states in bold face.,Some Oxidation States of Manganese,Aqueous oxoanions of transition elements.,One of the most characteristic chemical properties of these elements is the occurrence of multiple oxidation states.,4.Most transition metal compounds are colored,because the typical transition metal ion in a complex can absorb visible light of specific wavelengths due to an unpaired d-orbital electron or electrons(exceptions:MnO4-is purple and CrO4-2 is yellow).Complementary colors appear in the color wheel shown below:We can see from the color wheel that,if for instance,a substance looks blue(as does copper(II)sulfate solution),then it is absorbing orange light(580 to 620 nm).Transitions between d-orbitals or between the ligands and the metal atom in complexes give rise to color.Moreover,transition metal compounds that do NOT exhibit color either have an empty d-orbital(Sc3+or Ti4+)or a filled one(Zn2+).,An artists wheel.,The bright colors of chromium(VI)compounds.,Colors of representative compounds of the Period 4 transition metals.,titanium oxide,sodium chromate,potassium ferricyanide,nickel(II)nitrate hexahydrate,zinc sulfate heptahydrate,scandium oxide,vanadyl sulfate dihydrate,manganese(II)chloride tetrahydrate,cobalt(II)chloride hexahydrate,copper(II)sulfate pentahydrate,Metal Complexes and Coordination CompoundsSpecies such as Co(NH3)5Cl+2 that are assemblies of a central metal ion bonded to a group of surrounding molecules or ions are called metal complexes or merely complexes.If the complex carries a net charge,it is generally called a complex ion.Compounds that contain complexes are known as coordination compounds.The molecules or ions that surround the metal ion in a complex are known as ligands.Ligands coordinate(or bond)to a metal atom or ion to form a coordinate covalent bond.Notice that this bond is different than an ordinary covalent bond(where electrons are shared between two joining species).In the coordinate covalent bond,both electrons used to generate the bond are property of the ligand and NOT the metal!A saturated complex fullfills the 18 e-rule.,Components of a coordination compound.,Ligands are normally either anions or neutral polar molecules.Every ligand has at least one unshared pair of valence electrons to donate.Furthermore,they can broken down into the following categories:Monodentate ligand examples:Bidentate ligand examples:,Polydentate ligand examples:When these ligands are bonded(chelated)to a particular metal,we can define the coordination number as the number of donor atoms to which the metal is bonded.,Some more Bidentate ligands:CO32-carbanatoNO3-nitratoSO42-sulfato,Names of monodentate:Aqua,ammine,fluoro,chloro,cyano,thiocyano,hydroxo,nitro,Consider each coordination complex listed below and answer the following questions.What is the oxidation state of the metal?What is the total number of valence electrons around the metal?Determine the coordination number for each complex.D.Is the complex saturated or unsaturated?E.Are any ligands polydentate?If so,identify these ligands.1.CoCl2(en)2+5.Cr(edta)-2.Cr(ox)33-3.ZnCl42-4.Ni(CN)53-,Naming Coordination Compounds1.In naming salts,the name of the cation is given before the name of the anion.For example,in Co(NH3)5ClCl2,we name Co(NH3)5Cl2+before Cl-.2.Within a complex ion or molecule,the ligands are named before the metal.Ligands are listed in alphabetical order,regardless of charge on the ligand.Prefixes(see Rule#4 below)that give the number of ligands are NOT considered part of the ligand name in determining alphabetical order.Consider once again the Co(NH3)5Cl2+ion.Name the ammonia ligand first,then the chloride,followed by the metal:pentaamminechlorocobalt(III).,3.The names of the anionic ligands end in the letter“o”,whereas neutral ones ordinarily bear the name of the molecules.Special names are given for H2O(aqua),NH3(ammine),CO(carbonyl),and NO(nitrosyl).For example,Fe(CN)2(NH3)2(H2O)2+would be named diamminediaquadicyanoiron(III)ion.4.Greek prefixes(di,tri,tetra,penta,and hexa)are used to indicate the number of each kind of ligand when more than one is present as shown in the examples above.If the ligand already contains a Greek prefix(as in ethylenediamine)or if it is polydentate(i.e.able to attach at more than one binding site),then the following prefixes are used instead:2:bis-3:tris-4:tetrakis-,5.If the complex is an anion,its name ends in ate.If the symbol of the metal originates from a Latin name,then the Latin stem is used insteadFor example,the compound K4Fe(CN)6 is named potassium hexacyanoferrate(II).Common Latin stem listings(in parentheses):Copper(cuprate);iron(ferrate);tin(stannate);lead(plumbate).6.The oxidation number of the metal is given in parentheses in Roman numerals directly following the name of the metal.,PROBLEM:,SOLUTION:,Writing Names and Formulas of Coordination Compounds,(a)What is the systematic name of Na3AlF6?,(b)What is the systematic name of Co(en)2Cl2NO3?,(c)What is the formula of tetraaminebromochloroplatinum(IV)chloride?,(d)What is the formula of hexaaminecobalt(III)tetrachloro-ferrate(III)?,(a)The complex ion is AlF6 3-,Six(hexa-)fluorines(fluoro-)are the ligands-hexafluoro,Aluminum is the central metal atom-aluminate,Aluminum has only the+3 ion so we dont need Roman numerals.,sodium hexafluoroaluminate,Writing Names and Formulas of Coordination Compounds,(b)There are two ligands,chlorine and ethylenediamine-dichloro,bis(ethylenediamine),The complex is the cation and we have to use Roman numerals for the cobalt oxidation state since it has more than one-(III),The anion,nitrate,is named last.,dichlorobis(ethylenediamine)cobalt(III)nitrate,4 NH3,Br-,Cl-,Cl-,Pt4+,Pt(NH3)4BrClCl2,6 NH3,Co3+,4 Cl-,Fe3+,Co(NH3)6Cl4Fe3,Name/draw each of the following compounds listed below:A.NH4PtCl3(NH3)B.Co(NH3)6AuCl42C.Cr(OH)2(NH3)4BrD.Co(en)33+E.Na2PtCl2(ox)2F.FeOH(H2O)5Cl2G.Sodium tetrahydroxoaluminateH.potassium hexacyanoferrate(II)I.Dicarbonatodifluorocobalt(III)perchlorateJ.hexapyridinenickel(II)bromide,Coordination Compounds and their IsomersThe geometry(or shape)of a transition metal complex depends on the coordination number and nature of the metal ion.The following table outlines the various typical geometries along with examples of each:Coordination Number ShapeExamples2Linear CuCl2-,Ag(NH3)2+,AuCl2-4 Square PlanarMost d8 metal ions(some can be tetrahedral);Ni(CN)42-,PdCl42-4 Tetrahedral Most d10 metal ions;Cu(CN)43-,CdCl42-6 Octahedral Ti(H2O)63+,Co(en)33+Make sure and note the similarity with the molecular shapes in VSEPR theory.,Valence Bond TheoryRecall valence bond theory from last semester,where atomic orbitals mix to form molecular orbitals,and hybrization(or hybrid orbitals)results.(sp linear,sp2 trigonal planar,&sp3 tetrahedral).In ordinary covalent compounds the orbitals overlap with one(1)from each atom.Atomic Orbital Set Hybrid Orbital Set Electronic Geometrys,p Two sp Linears,p,pThree sp2Trigonal Planars,p,p,pFour sp3 Tetrahedrals,p,p,p,dFive sp3d Trigonal Bipyramidals,p,p,p,d,dSix sp3d2 Octahedral,Valence Bond Theory for Coordination ComplexesThe ligands(Lewis Bases)donate electrons to the metal(Lewis Acids)to form the covalent bond in the complex resulting in a mixing of the s,p,&d orbitals of the metal.In coordinate covalent bonds the ligand orbital(containing 2 e-s)overlaps with the UNOCCUPIED orbital of the metal.The number&type of metal ion hybrid orbital occupied by the ligands lone pair of electrons determines the geometry of the complex.,Valence Bond TheoryCr(NH3)63+Hexaamminechromium(III)ion a yellow complex is paramagnetic,use valence bond theory to explain the bonding and magnetic properties of the complex.d3 _ _ _(p)_(s)Cr3+_ _ _ _ _(d)and consider 6:NH3 therefore need 6 equivalent bonds!hybridization:_ _ _:d d d d d s p p pThe 3d metal electrons are unhybridized thus paramagnetic and the ligand electrons fit into the leftover hybridized d2sp3 orbitals of the metal.CN=6 thus octahedral,Hybrid orbitals and bonding in the octahedral Cr(NH3)63+ion.,Valence Bond TheoryNi(CN)42-Use valence bond theory to explain the bonding and magnetic properties of the above complex.d8 _ _ _(p)_(s)Ni2+_ _ _ _ _(d)and consider 4:CN therefore need 4 equivalent bonds!hybridization:_ _ _ _:_ d d d d d s p p pThe 3d metal electrons are unhybridized thus diamagnetic and the ligand electrons fit into the leftover hybridized dsp2 orbitals of the metal.CN=4 and square planar.Describe Zn(OH)42-,Hybrid orbitals and bonding in the square planar Ni(CN)42-ion.,Hybrid orbitals and bonding in the tetrahedral Zn(OH)42-ion.,Important types of isomerism in coordination compounds.,Atoms connected differently,Different spatial arrangement,C