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AN INTRODUCTION TO TRANSITION METAL CHEMISTRY KNOCKHARDY PUBLISHING 2008 SPECIFICATIONS.

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Presentation on theme: "AN INTRODUCTION TO TRANSITION METAL CHEMISTRY KNOCKHARDY PUBLISHING 2008 SPECIFICATIONS."— Presentation transcript:

1 AN INTRODUCTION TO TRANSITION METAL CHEMISTRY KNOCKHARDY PUBLISHING 2008 SPECIFICATIONS

2 INTRODUCTION This Powerpoint show is one of several produced to help students understand selected topics at AS and A2 level Chemistry. It is based on the requirements of the AQA and OCR specifications but is suitable for other examination boards. Individual students may use the material at home for revision purposes or it may be used for classroom teaching if an interactive white board is available. Accompanying notes on this, and the full range of AS and A2 topics, are available from the KNOCKHARDY SCIENCE WEBSITE at... www.knockhardy.org.uk/sci.htm Navigation is achieved by... either clicking on the grey arrows at the foot of each page orusing the left and right arrow keys on the keyboard KNOCKHARDY PUBLISHING TRANSITION METALS

3 CONTENTS Definition Metallic properties Electronic configurations Variable oxidation state Coloured ions Complex ion formation Shapes of complexes Isomerism in complexes Catalytic properties TRANSITION METALS

4 Before you start it would be helpful to… Recall the definition of a co-ordinate (dative covalent) bond Recall how to predict the shapes of simple molecules and ions TRANSITION METALS

5 THE FIRST ROW TRANSITION ELEMENTS DefinitionD-block elements forming one or more stable ions with partially filled (incomplete) d-sub shells. The first row runs from scandium to zinc filling the 3d orbitals. Properties arise from an incomplete d sub-shell in atoms or ions

6 THE FIRST ROW TRANSITION ELEMENTS DefinitionD-block elements forming one or more stable ions with partially filled (incomplete) d-sub shells. The first row runs from scandium to zinc filling the 3d orbitals. Properties arise from an incomplete d sub-shell in atoms or ions Metallic propertiesall the transition elements are metals strong metallic bonds due to small ionic size and close packing higher melting, boiling points and densities than s-block metals K Ca Sc Ti V Cr Mn Fe Co m. pt / °C 63 850 1400 1677 1917 1903 1244 1539 1495 density / g cm -3 0.86 1.55 3 4.5 6.1 7.2 7.4 7.9 8.9

7 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS POTASSIUM 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 In numerical terms one would expect the 3d orbitals to be filled next. However, because the principal energy levels get closer together as you go further from the nucleus coupled with the splitting into sub energy levels, the 4s orbital is of a LOWER ENERGY than the 3d orbitals so gets filled first. ‘Aufbau’ Principle INCREASING ENERGY / DISTANCE FROM NUCLEUS

8 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS CALCIUM 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 As expected, the next electron in pairs up to complete a filled 4s orbital. This explanation, using sub levels fits in with the position of potassium and calcium in the Periodic Table. All elements with an -s 1 electronic configuration are in Group I and all with an -s 2 configuration are in Group II. INCREASING ENERGY / DISTANCE FROM NUCLEUS

9 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS SCANDIUM 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1 With the lower energy 4s orbital filled, the next electrons can now fill p the 3d orbitals. There are five d orbitals. They are filled according to Hund’s Rule. BUT WATCH OUT FOR TWO SPECIAL CASES. INCREASING ENERGY / DISTANCE FROM NUCLEUS

10 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS TITANIUM 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 2 The 3d orbitals are filled according to Hund’s rule so the next electron doesn’t pair up but goes into an empty orbital in the same sub level. HUND’S RULE OF MAXIMUM MULTIPLICITY HUND’S RULE OF MAXIMUM MULTIPLICITY INCREASING ENERGY / DISTANCE FROM NUCLEUS

11 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS VANADIUM 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 3 The 3d orbitals are filled according to Hund’s rule so the next electron doesn’t pair up but goes into an empty orbital in the same sub level. HUND’S RULE OF MAXIMUM MULTIPLICITY HUND’S RULE OF MAXIMUM MULTIPLICITY INCREASING ENERGY / DISTANCE FROM NUCLEUS

12 4s 3 3p 3d 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS CHROMIUM 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 5 One would expect the configuration of chromium atoms to end in 4s 2 3d 4. To achieve a more stable arrangement of lower energy, one of the 4s electrons is promoted into the 3d to give six unpaired electrons with lower repulsion.

13 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS MANGANESE 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5 The new electron goes into the 4s to restore its filled state. INCREASING ENERGY / DISTANCE FROM NUCLEUS

14 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS IRON 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 Orbitals are filled according to Hund’s Rule. They continue to pair up. HUND’S RULE OF MAXIMUM MULTIPLICITY HUND’S RULE OF MAXIMUM MULTIPLICITY INCREASING ENERGY / DISTANCE FROM NUCLEUS

15 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS COBALT 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 7 Orbitals are filled according to Hund’s Rule. They continue to pair up. HUND’S RULE OF MAXIMUM MULTIPLICITY HUND’S RULE OF MAXIMUM MULTIPLICITY INCREASING ENERGY / DISTANCE FROM NUCLEUS

16 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS NICKEL 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 8 Orbitals are filled according to Hund’s Rule. They continue to pair up. HUND’S RULE OF MAXIMUM MULTIPLICITY HUND’S RULE OF MAXIMUM MULTIPLICITY INCREASING ENERGY / DISTANCE FROM NUCLEUS

17 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS COPPER 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 10 One would expect the configuration of copper atoms to end in 4s 2 3d 9. To achieve a more stable arrangement of lower energy, one of the 4s electrons is promoted into the 3d. HUND’S RULE OF MAXIMUM MULTIPLICITY HUND’S RULE OF MAXIMUM MULTIPLICITY INCREASING ENERGY / DISTANCE FROM NUCLEUS

18 4s 3 3p 3d 4 4p 4d 4f ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS ZINC 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 The electron goes into the 4s to restore its filled state and complete the 3d and 4s orbital filling. INCREASING ENERGY / DISTANCE FROM NUCLEUS

19 K1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Ca1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 Sc1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1 Ti1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 2 V1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 3 Cr1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 5 Mn1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5 Fe1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 Co1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 7 Ni1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 8 Cu1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 3d 10 Zn1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 ELECTRONIC CONFIGURATIONS

20 VARIABLE OXIDATION STATES Arises from the similar energies required for removal of 4s and 3d electrons When electrons are removed they come from the 4s orbitals first Cu1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 1 Ti1s 2 2s 2 2p 6 3s 2 3p 6 3d 2 4s 2 Cu + 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 Ti 2+ 1s 2 2s 2 2p 6 3s 2 3p 6 3d 2 Cu 2+ 1s 2 2s 2 2p 6 3s 2 3p 6 3d 9 Ti 3+ 1s 2 2s 2p6 3s 2 3p 6 3d 1 Ti 4+ 1s 2 2s 2 2p 6 3s 2 3p 6 maximum rises across row to manganese maximum falls as the energy required to remove more electrons becomes very high all (except scandium) have an M 2+ ion stability of +2 state increases across the row due to increase in the 3rd Ionisation Energy THE MOST IMPORTANT STATES ARE IN RED TiScVCrMnFeCoNiCuZn +1 +2 +3 +4 +5 +6 +2 +6 +7 +3 +4 +3 +4 +3 +4 +5 +6

21 COLOURED IONS Theory ions with a d 10 (full) or d 0 (empty) configuration are colourless ions with partially filled d-orbitals tend to be coloured it is caused by the ease of transition of electrons between energy levels energy is absorbed when an electron is promoted to a higher level the frequency of light is proportional to the energy difference ions with d 10 (full) Cu +,Ag + Zn 2+ or d 0 (empty) Sc 3+ configuration are colourless e.g. titanium(IV) oxide TiO 2 is white colour depends on... transition element oxidation state ligand coordination number A characteristic of transition metals is their ability to form coloured compounds

22 3d ORBITALS There are 5 different orbitals of the d variety z2z2 x 2 -y 2 xyxzyz

23 SPLITTING OF 3d ORBITALS Placing ligands around a central ion causes the energies of the d orbitals to change Some of the d orbitals gain energy and some lose energy In an octahedral complex, two (z 2 and x 2 -y 2 ) go higher and three go lower In a tetrahedral complex, three (xy, xz and yz) go higher and two go lower Degree of splitting depends on theCENTRAL ION and the LIGAND The energy difference between the levels affects how much energy is absorbed when an electron is promoted. The amount of energy governs the colour of light absorbed. 3d OCTAHEDRALTETRAHEDRAL

24 COLOURED IONS Absorbed colournmObserved colournm VIOLET400GREEN-YELLOW560 BLUE450YELLOW600 BLUE-GREEN490RED620 YELLOW-GREEN570VIOLET410 YELLOW580DARK BLUE430 ORANGE600BLUE450 RED650GREEN520 The observed colour of a solution depends on the wavelengths absorbed Copper sulphate solution appears blue because the energy absorbed corresponds to red and yellow wavelengths. Wavelengths corresponding to blue light aren’t absorbed. WHITE LIGHT GOES IN SOLUTION APPEARS BLUE ENERGY CORRESPONDING TO THESE COLOURS IS ABSORBED

25 COLOURED IONS a solution of copper(II)sulphate is blue because red and yellow wavelengths are absorbed white light blue and green not absorbed

26 COLOURED IONS a solution of copper(II)sulphate is blue because red and yellow wavelengths are absorbed

27 COLOURED IONS a solution of copper(II)sulphate is blue because red and yellow wavelengths are absorbed

28 COLOURED IONS a solution of nickel(II)sulphate is green because violet, blue and red wavelengths are absorbed

29 WHITE LIGHT BLUE FILTER RED LIGHT SOLUTION COLORIMETER FINDING COMPLEX ION FORMULAE USING COLORIMETRY a change of ligand can change the colour of a complex this property can be used to find the formula of a complex ion ight of a certain wavelength is passed through a solution the greater the colour intensity, the greater the absorbance the concentration of each species in the complex is altered the mixture with the greatest absorbance identifies ratio of ligands and ions

30 FINDING COMPLEX ION FORMULAE USING COLORIMETRY a change of ligand can change the colour of a complex this property can be used to find the formula of a complex ion ight of a certain wavelength is passed through a solution the greater the colour intensity, the greater the absorbance the concentration of each species in the complex is altered the mixture with the greatest absorbance identifies ratio of ligands and ions Finding the formula of an iron(III) complex White light is passed through a blue filter. The resulting red light is passed through mixtures of an aqueous iron(III) and potassium thiocyanate solution. Maximum absorbance occurs first when the ratio of Fe 3+ and SCN¯ is 1:1. This shows the complex has the formula [Fe(H 2 O) 5 SCN] 2+

31 FINDING COMPLEX ION FORMULAE USING COLORIMETRY a change of ligand can change the colour of a complex this property can be used to find the formula of a complex ion ight of a certain wavelength is passed through a solution the greater the colour intensity, the greater the absorbance the concentration of each species in the complex is altered the mixture with the greatest absorbance identifies ratio of ligands and ions Finding the formula of an nickel(II) edta complex Filtered light is passed through various mixtures of an aqueous solution of nickel(II) sulphate and edta solution. The maximum absorbance occurs when the ratio of Ni 2+ and edta is 1:1.

32 COMPLEX IONS - LIGANDS Formation ligands form co-ordinate bonds to a central transition metal ion Ligandsatoms, or ions, which possess lone pairs of electrons form co-ordinate bonds to the central ion donate a lone pair into vacant orbitals on the central species Ligand Formula Name of ligand chlorideCl¯chloro cyanideNC¯cyano hydroxideHO¯hydroxo oxideO 2- oxo waterH 2 Oaqua ammoniaNH 3 ammine some ligands attach themselves using two or more lone pairs classified by the number of lone pairs they use multidentate and bidentate ligands lead to more stable complexes

33 COMPLEX IONS - LIGANDS some ligands attach themselves using two or more lone pairs classified by the number of lone pairs they use multidentate and bidentate ligands lead to more stable complexes Unidentateform one co-ordinate bond Cl¯, OH¯, CN¯, NH 3, and H 2 O Bidentateform two co-ordinate bonds H 2 NCH 2 CH 2 NH 2, C 2 O 4 2-

34 COMPLEX IONS - LIGANDS some ligands attach themselves using two or more lone pairs classified by the number of lone pairs they use multidentate and bidentate ligands lead to more stable complexes Multidentateform several co-ordinate bonds EDTA An important complexing agent

35 COMPLEX IONS - LIGANDS some ligands attach themselves using two or more lone pairs classified by the number of lone pairs they use multidentate and bidentate ligands lead to more stable complexes Multidentateform several co-ordinate bonds HAEM A complex containing iron(II) which is responsible for the red colour in blood and for the transport of oxygen by red blood cells. Co-ordination of CO molecules interferes with the process

36 COMPLEX IONS - LIGANDS some ligands attach themselves using two or more lone pairs classified by the number of lone pairs they use multidentate and bidentate ligands lead to more stable complexes Multidentateform several co-ordinate bonds

37 CO-ORDINATION NUMBER & SHAPE the shape of a complex is governed by the number of ligands around the central ion the co-ordination number gives the number of ligands around the central ion a change of ligand can affect the co-ordination number Co-ordination No.ShapeExample(s) 6Octahedral[Cu(H 2 O) 6 ] 2+ 4Tetrahedral [CuCl 4 ] 2- Square planarPt(NH 3 ) 2 Cl 2 2Linear[Ag(NH 3 ) 2 ] +

38 ISOMERISATION IN COMPLEXES Some octahedral complexes can exist in more than one form [MA 4 B 2 ] n+ [MA 3 B 3 ] n+ TRANSCIS

39 ISOMERISATION IN COMPLEXES GEOMETRICAL (CIS-TRANS) ISOMERISM Square planar complexes of the form [MA 2 B 2 ] n+ exist in two forms trans platincis platin An important anti-cancer drug. It is a square planar, 4 co-ordinate complex of platinum.

40 ISOMERISATION IN COMPLEXES Octahedral complexes with bidentate ligands can exist as a pair of enantiomers (optical isomers) OPTICAL ISOMERISM Some octahedral complexes exist in two forms

41 ISOMERISATION IN COMPLEXES OPTICAL ISOMERISM OPTICAL ISOMERISM AND GEOMETRICAL ISOMERSIM The complex ion [Co(en) 2 Cl 2 ] + exhibits both types of isomerism

42 ISOMERISATION IN COMPLEXES OPTICAL ISOMERISM OPTICAL ISOMERISM AND GEOMETRICAL ISOMERSIM The complex ion [Co(en) 2 Cl 2 ] + exhibits both types of isomerism GEOMETRICAL ISOMERISM CIS TRANS

43 CATALYTIC PROPERTIES Transition metals and their compounds show great catalytic activity It is due to partly filled d-orbitals which can be used to form bonds with adsorbed reactants which helps reactions take place more easily Examples of catalysts IRONManufacture of ammonia - Haber Process NICKELHydrogenation reactions - margarine manufacture RHODIUMCatalytic converters VANADIUM(V) OXIDEManufacture of sulphuric acid - Contact Process

44 © 2009 JONATHAN HOPTON & KNOCKHARDY PUBLISHING THE END AN INTRODUCTION TO TRANSITION METAL CHEMISTRY


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