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1 of 35 © Boardworks Ltd 2007 2 of 35 © Boardworks Ltd 2007 What are the transition elements? The transition elements are d-block elements which form one or more stable ions with incomplete d subshell electrons. group 2 group 3 A transition element forms at least one ion with a partially-filled d-subshell Sc Ti V Cr Mn Fe Co Ni Cu Zn Y Zr Nb Mo Tc Ru Rh Pd Ag Cd La Hf Ta W Re Os Ir Pt Au Hg Here, the word ‘transition’ is used to mean ‘in-between’. Ac Rf Db Sg Bh Hs Mt Ds Rg ? 3 of 35 © Boardworks Ltd 2007 Uses of coloured trans. metal compounds The coloured compounds of transition metals can also be used in many ways, for example: to colour stained glass windows to colour paints as coloured glazes on pottery. 4 of 35 © Boardworks Ltd 2007 What are the uses of the transition metals? 5 of 35 © Boardworks Ltd 2007 Catalysis • Catalysis plays an essential aspect in about 90% of all chemical manufacturing. • Ni and Pt are very heterogeneous catalysts. • Pt, Rh, and Pd are used in catalytic converters. • V2O5 is used in conversion of SO2 to SO3. • Polyethylene is formed catalytically. Prentice-Hall © 2002 6 of 35 General Chemistry: Chapter 24 Slide 6 of 47 © Boardworks Ltd 2007 First row d-block elements Elements Atomic num. Sc 21 Ti V Cr Mn 22 23 24 25 Fe Co Ni 26 27 28 Cu Zn 29 30 7 of 35 Electronic Configuration [Ar] … [Ar] 3d1 4s2 © Boardworks Ltd 2007 Most common oxidation state Elements Sc Electronic Configuration [Ar] 3d1 4s2 Known oxidation state +3 Ti V Cr Mn [Ar] 3d2 4s2 [Ar] 3d3 4s2 [Ar] 3d5 4s1 [Ar]3d5 4s2 +3, +4 +2, +3, +4, +5 +3, +6 +2, +4, +6, +7 Fe Co Ni [Ar] 3d6 4s2 [Ar] 3d7 4s2 [Ar] 3d8 4s2 +2, +3 +2, +3 +2 Cu Zn [Ar] 3d10 4s1 [Ar] 3d10 4s2 +1, +2 +2 8 of 35 © Boardworks Ltd 2007 Write the electron configuration of 3+ •Cr 2+ •Cu 9 of 35 © Boardworks Ltd 2007 exercise • Explain why scandium (III) and zinc (II) cations are not called transition elements. • Why is the maximum oxidation state of manganese +7? • In the higher oxidation states, the elements exist as covalently bonded oxocompounds rather than atomic ions. Explain this phenomenon 10 of 35 © Boardworks Ltd 2007 Characteristic of transitional metals on their compounds • Variable oxidation state Due to similar energy of 4s and 3d • Formation of coloured ions / complex ions Due to electrons transition between d-orbitals • Catalytic activity Provide alternative reaction mechanism with lower activation energy • Paramagnetism Unpaired or odd electrons 11 of 35 © Boardworks Ltd 2007 What are the properties of the transition metals? The transition metals are known as ‘typical’ metals because of their physical properties. They are: lustrous (bright and shiny). hard and strong. high density. malleable (can be bent and pressed into different shapes) and ductile (can be drawn into wires). good conductors of heat and electricity. high melting and boiling points (except mercury, which is liquid at room temperature). 12 of 35 © Boardworks Ltd 2007 Color and Magnetism Prentice-Hall © 2002 13 of 35 General Chemistry: Chapter 24 Slide 13 of 47 © Boardworks Ltd 2007 Comparing properties of different metals How do the properties of transition metals compare with those of alkali metals? Compared to the alkali metals, the transition metals: are harder and stronger. They cannot be cut with a knife. are more dense. This means that in a fixed volume of metal there are more atoms of a transition metal than there are of an alkali metal. have higher melting and boiling points – except mercury. 14 of 35 © Boardworks Ltd 2007 Comparing densities of metals 15 of 35 © Boardworks Ltd 2007 Comparing melting points of metals 16 of 35 © Boardworks Ltd 2007 True or false? 17 of 35 © Boardworks Ltd 2007 Redox reactions • A positive Ecell indicates a thermodynamically feasible reaction • A negative Ecell indicates a thermodynamically non-feasible reaction 18 of 35 © Boardworks Ltd 2007 • Judging from Ecell [ data booklet ] o Predict the outcome of mixing aqueous iron(II) with chlorine. o Predict the outcome of mixing acidified tin (II) with hydrogen peroxide (H2O2) o Which one is the better oxidising agent in acidified solution : KMnO4 or K2Cr2O7 to oxidized solution of iron(II) 19 of 35 © Boardworks Ltd 2007 Complex ions • A compound in which ligand molecules form (dative) co-ordinate bonds to a centre metal atom or ion. • Ligand :a ion or molecule that has at least a lone pair of electrons available for donation to the central metal atom or ion. 20 of 35 © Boardworks Ltd 2007 How to write a complex structure 21 of 35 © Boardworks Ltd 2007 Features of complex ions • Net charge on complex ions Net charge Oxidation number Knowing the charge on a complex ion and the charge on each ligand, one can determine the oxidation number for the metal. 22 of 35 © Boardworks Ltd 2007 Features of complex ions • In a compound, complex ion attaches to a counter ion. K4[Fe(CN)6] Na2CuCl4 [Cu(NH3)4]SO4 23 of 35 © Boardworks Ltd 2007 Features of complex ions • Co-ordination number (number of dative bonds attached) 24 of 35 © Boardworks Ltd 2007 Ligands • Neutral H2O, NH3, CO, amines, etc • Ionic Cl-, CN-, etc 25 of 35 © Boardworks Ltd 2007 26 of 35 © Boardworks Ltd 2007 Types of ligands • Based on number of dative bonds: o Monodentate [ one dative bond ] o H2O, NH3, halide, CN-, CO o Bidentate [ two dative bonds ] o Ethylenediamine, oxalate ions o Polydentate [ more than two dative bonds ] o EDTA (EthyleneDiamineTetraAcetate ion) 27 of 35 © Boardworks Ltd 2007 28 of 35 © Boardworks Ltd 2007 chelate • Bidentate or polydentate ligands that form ring in a complex ion. – Ethane-1,2-diamine [“en”] – Ethanedioate ions [“ox”] – EDTA 29 of 35 © Boardworks Ltd 2007 Rule for naming complex ions • Complex cation – Names of ligands are given first, then the central ion with its oxidation state in brakets – Ligands are named in alphabetical order with suitable prefix to indicate number of ligand present [di, tri, tetra, etc] – The ligand and central ion are named without space • Complex anion – Similar method, except central metal ion is altered to end in -ate 30 of 35 © Boardworks Ltd 2007 Ligands H2O NH3 Name aqua F- ammine fluoro Cl- CN- SCN- OH- chloro cyano thiocyanate Hydroxo These are strong ligands Cationic complexes Anionic complexes Titanium Titanate 31 of 35 vanadium Manganese Iron Vanadate Manganate Ferrate Copper Cuprate © Boardworks Ltd 2007 Table 25.2 Some Common Monodentate Ligands. Prentice-Hall © 2002 32 of 35 General Chemistry: Chapter 25 Slide 32 of 55 © Boardworks Ltd 2007 Give names • • • • • • Cu(en)22+ Fe(Ox)33[Cu(H2O)6]2+ [Cr(NH3)5Cl]2+ [Fe(CN)6]4[Fe(H2O)6]2+ 33 of 35 • • • • [Cu(H2O)6]SO4 [Cr(NH3)5Cl]Cl2 K4[Fe(CN)6] [Fe(H2O)6](NO3)2 © Boardworks Ltd 2007 Ethylene Diamine Prentice-Hall © 2002 34 of 35 General Chemistry: Chapter 25 Slide 34 of 55 © Boardworks Ltd 2007 Copper complex in ligand substitution add ammonia solution Cu(H2O)62+ Co(NH3)4(H2O)22+ blue Add conc HCl deep blue / violet Add NaOH or NH3 (aq) CuCl42- Cu(OH)2 yellow-green pale blue 35 of 35 © Boardworks Ltd 2007 Substitution of ligands • Ligands can be exchange in the complex ions. Cu(H2O)62+ + 2OH- Cu(OH)2(H2O)4(s) + 2H2O pale blue Cu(OH)2(H2O)4(s) + 4NH3 [Cu(H2O)2(NH3)4]2+ + 2H2O + 2OHDeep blue 36 of 35 © Boardworks Ltd 2007 Metal Carbonyls Prentice-Hall © 2002 37 of 35 General Chemistry: Chapter 24 Slide 37 of 47 © Boardworks Ltd 2007 Shape of complex ions Coordination number Shape Hybridization Examples 2 4 4 Linear Tetrahedral Square planar Octahedral sp sp3 dsp2 [CuCl2][CuCl4][Ni(CN)4]2- sp3d2 [Fe(H2O)6]2+ 6 38 of 35 © Boardworks Ltd 2007 Orbital d 39 of 35 © Boardworks Ltd 2007 Oxidation States Prentice-Hall © 2002 40 of 35 General Chemistry: Chapter 24 Slide 40 of 47 © Boardworks Ltd 2007 Colour of complexes • Depends on: – The nature of the central metal ions – Oxidation state of the central metal ions – Types of ligands 41 of 35 © Boardworks Ltd 2007 Splitting of d orbitals 42 of 35 © Boardworks Ltd 2007 • The two d-orbitals [dx2-y2, and dz2] locate along axes causing a repulsion by the coming electron from the ligans, as to compare with the other d-orbitals [dxy, dyz, dxy] which locate in between axes having lower repulsion. • This causes d-orbitals to separate into 2 different energy levels. 43 of 35 © Boardworks Ltd 2007 Octahedral Complex and d-Orbital Energies Prentice-Hall © 2002 44 of 35 General Chemistry: Chapter 25 Slide 44 of 55 © Boardworks Ltd 2007 Electron Configuration in d-Orbitals Δ P Hund’s rule pairing energy considerations Δ>P low spin d4 Prentice-Hall © 2002 45 of 35 Δ<P high spin d4 General Chemistry: Chapter 25 Slide 45 of 55 © Boardworks Ltd 2007 The effect of types of ligand 46 of 35 © Boardworks Ltd 2007 Large Δ Strong field ligands CN- > NO2- > en > py NH3 > EDTA4- > SCN- > H2O > ONO- > ox2- > OH- > F- > SCN- > Cl- > Br- > I- Small Δ Weak field ligands 47 of 35 © Boardworks Ltd 2007 Transition between d-d* electron 48 of 35 © Boardworks Ltd 2007 49 of 35 © Boardworks Ltd 2007 50 of 35 © Boardworks Ltd 2007 Geometric Isomerism Prentice-Hall © 2002 51 of 35 General Chemistry: Chapter 25 Slide 51 of 55 © Boardworks Ltd 2007 conclusion • A substance appears coloured when certain wavelength of white light is absobed. The complementary wavelength [white light minus the colour absobed] gives the colour of the substance • Transition of electron(s) d-d* transition 52 of 35 © Boardworks Ltd 2007 Effect of Ligands on the Colors of Coordination Compounds Prentice-Hall © 2002 53 of 35 General Chemistry: Chapter 25 Slide 53 of 55 © Boardworks Ltd 2007 Homework • Explain the term homogeneous and heterogeneous catalyst. • Give examples and reactions for homogeneous and heterogeneous catalyst. • Compare, qualitatively, the melting point, density, atomic radius, ionic radius, first ionization energy and conductivity of the transition elements with those of calcium as a typical s-block element. 54 of 35 © Boardworks Ltd 2007 55 of 35 © Boardworks Ltd 2007 Glossary (1/2) alloy – A mixture of a metal and at least one other element. catalyst – A substance that increases the speed of a chemical reaction without being used up. corrosion – Damage to a metal caused by a chemical or reaction such as rusting. density – A measure of mass in a given volume. Often expressed in g/dm3. ductile – The ability of metals to be drawn into wires. lustrous – Bright and shiny. malleable – Capable of being bent and pressed into a different shape. 56 of 35 © Boardworks Ltd 2007 Glossary (2/2) precipitate – A solid that forms in a solution as a result of a physical or chemical reaction. thermal decomposition – The process by which a substance is broken down into two or more products by heating it. transition metal – An element located in the block between groups 2 and 3 of the periodic table. 57 of 35 © Boardworks Ltd 2007 Anagrams 58 of 35 © Boardworks Ltd 2007 Properties of transition metals 59 of 35 © Boardworks Ltd 2007 Multiple-choice quiz 60 of 35 © Boardworks Ltd 2007