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TR A N S IT IO N ME T A L S

TR A N S IT IO N ME T A L S. d block) and inner transition elements (f block). USES: Transition Metals. Titanium – structural material (light weight) Manganese – production of hard steel Iron – most abundant heavy metal Cobalt – alloys with other metals

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TR A N S IT IO N ME T A L S

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  1. TRANSITION METALS

  2. d block) and inner transition elements (f block)

  3. USES: Transition Metals • Titanium – structural material (light weight) • Manganese – production of hard steel • Iron – most abundant heavy metal • Cobalt – alloys with other metals • Copper – plumbing and electrical applications • Chromium is electroplated to make shiny metal ex: Stainless Steel = 73% Fe,18% Cr, 8% Ni, 1% C • Not these are mostly COLURLESS, but their ions are not as we will see

  4. FIRST ROW TRANSITION ELEMENTS Physical strong metallic bonds due to small ionic size and close packing Propertieshigher melting, boiling points s-block metals. Many are COLOURED. Ca ScTi V Cr Mn Fe Co m. pt / °C 850 1400 1677 1917 1903 1244 1539 1495 density / g cm-3 1.55 3.00 4.5 6.1 7.2 7.4 7.9 8.9 sodium chromate nickel(II) nitrate hexahydrate potassium ferricyanide zinc sulfate heptahydrate Titanium(IV) oxide scandium oxide manganese(II) chloride tetrahydrate copper(II) sulfate pentahydrate vanadyl sulfate dihydrate cobalt(II) chloride hexahydrate

  5. Scandium (Sc) and Zinc (Zn) Strictly speaking, scandium (Sc) and zinc (Zn) are not transitions elements Sc forms Sc3+ ion which has an empty d sub-shell (3d0) Zn forms Zn2+ ion which has a completely filled d sub-shell (3d10)

  6. ELECTRONIC CONFIGURATIONS (and some Ions) Note: Removing e- from the highest level of n FIRST(or largest number) Sc3+ 1s2 2s2 2p6 3s2 3p64s2 3d1 Sc 1s2 2s2 2p6 3s2 3p64s2 3d1 Ti 1s2 2s2 2p6 3s2 3p64s2 3d2 Chromium is an exception Cr 1s2 2s2 2p6 3s2 3p6 4s1 3d5 Mn 1s2 2s2 2p6 3s2 3p6 4s2 3d5 Fe 1s2 2s2 2p6 3s2 3p6 4s2 3d6 Co 1s2 2s2 2p6 3s2 3p6 4s2 3d7 Ni 1s2 2s2 2p6 3s2 3p6 4s2 3d8 Cu 1s2 2s2 2p6 3s2 3p6 4s1 3d10 Zn 1s2 2s2 2p6 3s2 3p6 4s2 3d10 Ti2+1s2 2s2 2p6 3s2 3p64s2 3d2 Ti3+ 1s22s2p63s23p64s2 3d2 goes to 3d1 Ti4+ 1s2 2s2 2p6 3s23p6 Mn can have 7 ions An exception Cu. 1s2 2s2 2p6 3s2 3p63d10 4s1 Cu+ 1s2 2s2 2p6 3s2 3p63d10 Cu2+ 1s2 2s2 2p6 3s2 3p63d9 Zn2+ 1s2 2s2 2p6 3s2 3p64s2 3d10

  7. Variable oxidation state The relative stability of various oxidation states can be correlated -with the stability of empty, half-filled and fully- filled configuration e.g.Ti4+ is more stable than Ti3+ ([Ar]3d0 configuration) Mn2+ is more stable than Mn3+ ([Ar]3d5 configuration) Zn2+ is more stable than Zn+ ([Ar]3d10 configuration) 7

  8. GENERAL PROPERTIES The chemical properties of transition metals are: they form complexes, coloured ions, variable oxidation states, and have catalytic activity. All characteristic properties are a result of their electronic structure due to a partially filled 3d energy levels in their atoms or ions PROPERTIES OF TRANSITION METALS

  9. FORMING IONS To write the electronic structure for Co2+: [Ar] 3d7 The 2+ ion is formed by the loss of the two 4s electrons. To write the electronic structure for V3+: [Ar] 3d2 4s electrons are always removed first 3d electrons are only removed after all 4s electrons have been removed

  10. SHAPES OF COMPLEXES • The co-ordination number dictates the shape of the complex • This is the number of coordinate bonds formed with the central metal ion • 2 co-ordinate = linear • 4 co-ordinate = tetrahedral or square planar • 6 co-ordinate = octahedral

  11. Copper • Cu shows some intermediate behaviour between transition and non-transition elements because of two oxidation states, Cu(I) & Cu(II) • Cu+ is not a transition metal ion as it has a completely filled d sub-shell • Cu2+ is a transition metal ion as it has an incompletely filled d sub-shell 11

  12. General Features Transition Metals Variations in atomic and ionic radii of the first series of d-block elements 12

  13. General Features Transition Metals • The atomic size reduces at the beginning of the series • increase in effective nuclear charge with atomic numbers •  the electron clouds are pulled closer to the nucleus •  causing a reduction in atomic size • The atomic size decreases slowly in the middle of the series • when more and more electrons enter the inner 3d sub-shell •  the screening and repulsive effects of the electrons in the 3d sub-shell increase •  the effective nuclear charge increases slowly

  14. Iron is used to make ships General Features Transition Metals Ramstore Bridge (Astana) - constructed using steel 14

  15. Nomenclature of Complexes The root names of anionic ligands always end in -o. e.g. CN– cyano Cl– chloro The names of neutral ligands are the names of the molecules, except NH3, H2O, CO and NO e.g. NH3 ammine, and H2O is aqua, CO is Cabonyl (see below) ( see below)

  16. Nomenclature of Complexes The number of each type of ligands are specified by the Greek prefixes: mono-, di-, tri-, tetra-, penta-, hexa-, etc. The oxidation number of the metal ion in the complex is named immediately after it by Roman numerals Therefore, K3[Fe(CN)6] potassium hexacyanoferrate(III) [CrCl2(H2O)4]Cl dichlorotetraaquachromium(III) chloride [CoCl3(NH3)] trichlorotriamminecobalt(III) Note: in the formulae, the complexes are always enclosed in [ ] 16

  17. Nomenclature of Complexes If it is anionic, then the suffix -ate is attached K2CoCl4 = potassium tetrachlorocobaltate(II) K3Fe(CN)6 potassium hexacyanoferrate(III) [CuCl4]2– tetrachlorocuprate(II) ion (b) If the complex is cationic or neutral, then the metal is unchanged. e.g. [CrCl2(H2O)4]+ dichlorotetraaquachromium(III) ion [CoCl3(NH3)3] trichlorotriamminecobalt(III)

  18. Nomenclature of Complexes Examples: 1. Ionic complexes

  19. Nomenclature of Complexes 2. Neutral complex

  20. COMPLEX FORMATION Check Point • Work out the oxidation states (OS) and co-ordination numbers (CN) of the following complexes: • [Cu(H2O)6]2+ OS: +2 CN:6 • [Ag(NH3)2]+ OS: +1 CN:2 • [Cu(NH3)4]2+ OS: +2 CN:4 • [Cu(Cl)4]2-OS: +2 CN:4 • [Fe(CN)6]3- OS: +3 CN:6

  21. Writing Names and Formulas of Coordination Compounds PROBLEM: (a) What is the systematic name of Na3[AlF6]? (b) What is the formula of tetraaminebromochloroplatinum(IV) chloride? (c) What is the formula of hexaaminecobalt(III) bromide? SOLUTION: (a) The complex ion is [AlF6]3-. Six (hexa-) fluorines (fluoro-) are the ligands - hexafluoro Aluminum is the central metal atom – aluminate –ends in ATE because it is negative Aluminum has only the +3 ion so we don’t need Roman numerals. sodium hexafluoroaluminate

  22. (b) tetraamminebromochloroplatinum(IV) chloride (c) hexaamminecobalt(III) Bromide Writing Names and Formulas of Coordination Compounds 4 NH3 Br- Cl- Pt4+ Cl- [Pt(NH3)4BrCl]Cl2 6 NH3 Co3+ bromide [Co(NH3)6]Br3

  23. Try a few Formula Name [CuCl4]2- tetrachlorochromium (II) ion Formula Name [Cu(H2O)6]2+ Hexaaquacopper(II) ion

  24. PROBLEM: The alloy SmCo5 forms a permanent magnet because both samarium and cobalt have unpaired electrons. How many unpaired electrons are in the Sm atom (Z = 62)? 6s 4f Finding the Number of Unpaired Electrons SOLUTION: Sm is the 8th element after Xe. Two electrons go into the 6s sublevel and the remaining six electrons into the 4f (which fills before the 5d). Sm is [Xe]6s24f 6 There are 6 unpaired e− in Sm., the more UNPAIRED electrons, the more magnetic

  25. SHAPES OF COMPLEX IONS

  26. SHAPES OF COMPLEX IONS

  27. COMPLEX FORMATION Unidentate ligands – form one co-ordinate bond e.g. H2O: :OH- :NH3 :CN- :Cl- Question. Cu with water then with Cl-, what would it be? [CuCl4] 2- it is an anion -ate tetrachlorochromate(II) ion [Cu(H2O)6]2+ Hexaaquacopper(II) Shape: OCTAHEDRAL Shape TETRAHEDRAL

  28. COMPLEX FORMATION Bidentate ligands – form two co-ordinate bonds ethanedioate (C2O42-) 1,2-diaminoethane Or ethandiamine e.g. [Cr(NH2CH2CH2NH2)3]3+ e.g. [Cr(C2O4)3]3- O

  29. COMPLEX FORMATION Multidentate ligands – form several co-ordinate bonds EDTA4- Union of ethanediamine and tetra ethanoicacid e.g. can you name this ion [Co(EDTA)]2- ? Ethandiaminetetraacetocobalt(II)

  30. EDTA – A sexidentate ligand or 6 Claws ethylenediamminetetraacetate ion (EDTA4-), • Applications: As a chelating Agent ( chelating = claw ) • EDTA4- is used to "trap" trace amounts of transition metals that could potentially catalyze the decomposition of the product. • The sodium salt of EDTA4- (i.e., Na4EDTA) can be found in many commercial products including: • soap • beer • mayonnaise

  31. Summary COMPLEX FORMATION TERMS Ligand particle with a lone pair that forms co-ordinate bond to metal Complex metal ion with ligands co-ordinately bonded to it Co-ordination number number of co-ordinate bonds from ligand(s) to metal ions lone pair donor (ligands are Lewis bases) Eg:Cl- Lewis base Lewis acid lone pair acceptor Cu2+

  32. SUMMARY LIGANDS Ligands possess one or more lone pair of electrons Thus they are Lewis Bases Ligands form co-ordinate bonds to the central ion by donating a lone pair : into vacant orbitals on the central species Bidentate form two co-ordinate bonds H2NCH2CH2NH2 C2O42-

  33. Learning Objectives Understand, be able to predict the shape of, and be able to draw octahedral, tetrahedral and linear complexes Understand the reasons for the colours and colour changes which they undergo on reaction and be able to give a general description of this in terms of electronic transitions Understand and be able to use spectrometry to determine concentration Know that transition elements show variable oxidation states and be able to describe specified examples

  34. TRANSITION METALS Explainingcolour Using the key words: Absorbed, transmitted and reflected explain the colours in each of the following:

  35. Colour and the d-block Transition metal ions in solution are often coloured.

  36. Why are transition metals coloured? When white light falls on any substance, some may be absorbed, some transmitted and some reflected. If light in the visible region of the spectrum is absorbed then the compound will appear coloured. The light reflected is what we see.

  37. Colour Wheel - What will the colour be? Complementary colours If one colour is absorbed then the compound will appear the colour opposite it in the wheel

  38. Using the colour wheel predict the colour of the following transition metal ions Cr3+ (aq) absorbs yellow light and so is violet Fe3+ (aq) absorbs violet light and so is yellow Fe2+ (aq) absorbs red light and so is green Co2+ (aq) absorbs pale green light and is Pink (ok, off red) Cu2+ (aq) absorbs orange light and so is? Blue

  39. Interesting example Plutonium is a transition element – it too has very colourful ions in solution…

  40. Explaining the colour-ligand relationship [Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq) 2NH3 4NH3

  41. Explaining the colour-ligand relationship RBG [Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

  42. Explaining the colour-ligand relationship RBG BG [Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

  43. Explaining the colour-ligand relationship RBG RBG BG [Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

  44. Explaining the colour-ligand relationship RBG RBG BG B [Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

  45. Ligand field theory With no ligands present the 5 d-orbitals are of equal energy (degenerate) When the d-orbitals are surrounded by ligands their energy is split, due to the negative charge of the lone pair on the ligand causing repulsion Orbitals with lobes along the axes have their energy raised Orbitals with lobes between the axes have their energy lowered

  46. The spectrochemical series shows the relative abilities of some common ligands to split the d-orbital energy levels.

  47. Explain how the oxidation state of the transition metal and the transition metal's identity affect colour • The type of metal and the oxidation state both affect colour for the same reason: • Different metals (or a particular metal in different oxidation states) have different number of electrons in the d sub-shell • This causes the energy of the d-orbitals to split by different amounts

  48. Colour of complexes • From the preceding you should have realised that the colour of the complex depended on • 1) the changes in the? • type of ligand • Why? • Different ligands split the degeneracy of the d orbitals by different amounts

  49. Colour of complexes • As the electrostatic repulsion is different • Therefore the energy gap is different • and so the wavelength of visible light absorbed will change • Hence the colour changes • e.g. blue [Cu (H2O)6]2+to • [Cu (H2O)4(NH3)2]2+ dark blue

  50. Colour of complexes 2) the changes in the ox #? Hint e.g. blue [Cu (H2O)62+ ] octahedral to [CuCl4]2- yellow which is tetrahedral Co-ordination number Why? The order of the splitting is reversed so the energy gap is different etc.

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