1. Topic 15A The Principals of transition metals chemistry Lesson 1 Introduction to transition metals
Thursday, 15 November 2018

2. Introduction to transition metals
be able to deduce the electronic configurations of atoms and ions of the d-block elements of period 4 (Sc–Zn), given the atomic number and charge (if any)
know that transition metals are d-block elements that form one or more stable ions with incompletely-filled d-orbitals
understand why transition metals show variable oxidation number
know what is meant by the term ‘ligand’
understand that dative (coordinate) bonding is involved in the formation of complex ions
know that a complex ion is a central metal ion surrounded by ligands
understand the meaning of the term ‘coordination number’
understand why H2O, OH− and NH3 act as monodentate ligands
be able to identify bidentate ligands, such as NH2CH2CH2NH2 and multidentate ligands, such as EDTA4−

3. General Properties of Transition Metals
Do Now:
What do you know already about the transition metals?

4. What do we know about the d-block?
Transition metals
The outer e- are in the d sub-shell.
“Transition metals are d-block elements that form one or more stable ions with incompletely filled d-orbitals”
Why are Sc and Zn d-block elements, but NOT transition elements?
This slide is a repeat of one in the redox topic
Pupils should know that answer to the question.
Only Ti-Cu in the first row are transition metals.
Sc and Zn have e in the d sub-shell, but they do not form any stable ions with partially filled d sub-shell (Sc3+ would be 1s22s22p63s23p6)
(Zn2+ would be 1s22s22p63s23p63d10)
Sc1s22s22p63s23p63d14s2
Zn1s22s22p63s23p63d104s2

5. What are Transition Metals?
Transition metals form at least one stable ion with a partially filled d sub-shell.
Top row transition metals: Ti – Cu
According to the definition ...
Sc is not a transition metal (Sc and Sc3+)
Zn is not a transition metal (Zn and Zn2+)

6. Electronic Configurations
Task: Complete the electronic configurations for the following atoms and ions (Use shorthand notation e.g., [Ar] ...)
Remember!
4s fills and empties before 3d Fe
[Ar] 4s2 3d6 Cu
[Ar] 4s1 3d10
Fe3+
[Ar] 3d5
Cu+
[Ar] 3d10 Sc
This is on p2 of the TM Chemsheets booklet
Ask pupils to complete the rest of p2
Remind pupils about:
Cr [Ar] 4s1 3d5
Cu [Ar] 4s1 3d10
4s1 so that half or full d sub-shell ... More stable
[Ar] 4s2 3d1
Cu2+
[Ar] 3d9
Sc3+
[Ar] Zn
[Ar] 4s2 3d10 V
[Ar] 4s2 3d3
Zn2+
[Ar] 3d10
V2+
[Ar] 3d3 Cr
[Ar] 4s1 3d5

7. Characteristics of TM
They are all metals, so your task is to list their characteristics…
Hard
Strong
Shiny
High mpt and bpt
Good conductors of heat and electricity
Act as catalysts
Form coloured ions and compounds
Form ions with different oxidation states
Form ions with incompletely-filled d-orbitals
TM tend to be stronger , more dense and less reactive than the metals in Groups 1 and 2.

8. Uses of TM
Their physical properties together with their fairly low chemical reactivity make the TM very useful
Fe (and alloy steel) for vehicles and to reinforce concrete
Cu for water pipes
Ti for jet engine parts that need to withstand high temps

9. 1) They form coloured ions
The majority of TM complexes are coloured
e.g., Cu2+ (aq) is blue - CuSO4

10. 2) They form complexes (ligands form co-ordinate bonds to the metal ion)
[Cu(H2O)6]2+
[CuCl4]2-
[Cu(H2O)6]2+ formed when CuSO4 dissolves in water

11. 3) They exhibit variable oxidation states
Often have more than one oxidation state in their compounds, e.g., Cu(I) and Cu(II)
So they can take part in many redox reactions

12. Explaining the variable oxidation states in the transition metals
We'll look at the formation of simple ions like Fe2+ and Fe3+.
When a metal forms an ionic compound, the formula of the compound produced depends on the energetics of the process. On the whole, the compound formed is the one in which most energy is released. The more energy released, the more stable the compound.
There are several energy terms to think about, but the key ones are:
The amount of energy needed to ionise the metal (the sum of the various ionisation energies)
The amount of energy released when the compound forms. This will either be lattice enthalpy if you are thinking about solids, or the hydration enthalpies of the ions if you are thinking about solutions.
The more highly charged the ion, the more electrons you have to remove and the more ionisation energy you will have to provide.
But off-setting this, the more highly charged the ion, the more energy is released either as lattice enthalpy or the hydration enthalpy of the metal ion.
Page 49 cgp revision guide

13. 4) They show catalytic activity
Ni Margarine production
V2O5 Contact Process making SO3 for H2SO4
Fe Haber process to make NH3
Pt, Pd Catalytic converters
MnO2 Decomposition of H2O2
Question pupils on the catalysts – they should know Vanadium(V) oxide and iron from Unit 2

14. Oxidation States
What is the oxidation of the TM in the following compounds?
TiO3
CuSO4
KMnO4
CoSO4
V2O5
MnCl2
TiCl4
K2CrO4

15. Oxidation States
What is the oxidation of the TM in the following compounds?
Ti2O
CuSO
KMnO
CoSO
V2O
MnCl
TiCl
K2CrO

16. Questions on page 102 of the edexcel work book Page 102 of edexcel revision guide Page 49 of CGP revision guide

17. Quick Check: True or False
TM are very useful because they are generally more reactive than Group 1 and Group 2 metals.
The electronic configuration of Cr is [Ar] 4s2 3d4
Zn is not a TM
The oxidation state of vanadium is VCl3 is +3
The 4 chemical properties of TM are:
Catalysis, formation of coloured ion, formation of complex ions, formation of hydroxides in water

18. Quick Check: True or False
TM are very useful because they are generally more reactive than Group 1 and Group 2 metals.
The electronic configuration of Cr is [Ar] 4s2 3d4
Zn is not a TM
The oxidation state of vanadium is VCl3 is +3
The 4 chemical properties of TM are:
Catalysis, formation of coloured ion, formation of complex ions, formation of hydroxides in water

19. Introduction to transition metals
be able to deduce the electronic configurations of atoms and ions of the d-block elements of period 4 (Sc–Zn), given the atomic number and charge (if any)
know that transition metals are d-block elements that form one or more stable ions with incompletely-filled d-orbitals
understand why transition metals show variable oxidation number
know what is meant by the term ‘ligand’
understand that dative (coordinate) bonding is involved in the formation of complex ions
know that a complex ion is a central metal ion surrounded by ligands
understand the meaning of the term ‘coordination number’
understand why H2O, OH− and NH3 act as monodentate ligands
be able to identify bidentate ligands, such as NH2CH2CH2NH2 and multidentate ligands, such as EDTA4−

20. Complex Formation Do Now: What is a coordinate bond?
What is a covalent bond?
What does Fe3+(aq) mean?

21. What is a Complex? Some definitions ...
Ligand ion/ molecule with a lone pair that forms co-ordinate bond with a 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
Remind pupils of co-ordinate bonds – covalent bond where one atom donates BOTH electrons
Make it clear that Lewis acids and Lewis bases are NOT the same as Bronsted-Lowry acids and Bases (opposite way around and involve

22. Formation of complex
Transition metals have a smaller radii than non-transition metals
Due to the smaller radii, they can attract electron-rich species more strongly e.g. water molecules
The water molecules are attracted to the TM ions strongly so they form a specific number of bonds

24. Complexes
A complex is an ion or molecule with a central atom or ion surrounded by ligands joined by co-ordinate bonds so that the number of ligands exceeds the oxidation state of the central atom. e.g.,
[Cu(H2O)6]2+

25. Complexes
It is a well known fact that copper(II) sulphate is not a blue solid!
Anhydrous copper(II) sulphate is a white solid but becomes blue in solution because of the formation of this complex.
Cu2+ + 6H2O  [Cu(H2O)6] 2+
white(s) blue(aq)
Demo CuSO4 anhydrous and hydrated

26. Ligands These can be: Negative ions: Cl-, OH-, CN-
Uncharged molecules that have one or more lone pairs of e-:
NH3, H2O

27. Complexes 6 4 The co-ordination number of the complex is the number of
co-ordinate bonds attached to the central atom or ion.
[Cr(NH3)6]3+ co-ord no. =
[CuCl4]2- co-ord no. = 6 4
Be careful!
The coordination number is not defined as the number of ligands in a complex

28. Naming Complexes

29. Naming Complexes Formulas give us a lot of info ... [Cu(H2O)6]2+
[CuCl4]2-
Brackets:
() = ligands comprising more than 1 element (H2O, NH3, OH-, CN-). NOT needed if ligand is ion formed from 1 element.
[] = to enclose the complex. Overall charge on the outside.
Name also gives a lot of info ...
[Cu(H2O)6]2+ Overall charge = +2, central Cu ion, 6 water molecules as ligands, Cu ox state = +2
[CuCl4]2- Overall charge = -2, central Cu ion, 4 chloride ions as ligands, Cu ox state = +2

30. Naming Complexes Name gives info on ... Number of each type of ligand
The identity of each ligand
The identity of the central metal ion and its oxidation state

31. Overall Charge/Oxidation Number The overall charge on the complex ion is its oxidation number. It is outside of the square brackets. Oxidation number of the metal ion = Total oxidation number – sum of the charges of the ligands E.g. [Fe(CN)6]4- Total oxidation number is -4 and each CN- ligand has a charge of -1 Fe’s ox number = -4 – (6x-1) = +2

32. Naming Complexes Number of ligands Prefix 2 Di 3 Tri 4 Tetra 5 Penta 6
1. Number of each type of ligand
Number of ligands
Prefix 2 Di 3
Tri 4
Tetra 5
Penta 6
hexa

33. Naming Complexes Ligand Name in complex Water Aqua Ammonia Ammine
2. The identity of each ligand
Ligand
Name in complex
Water
Aqua
Ammonia
Ammine
Chloride
Chloro
Hydroxide
Hydroxo
cyanide
Cyano
Ammine is with 2 “m” – not to be confused with “amine”
Also Diammine and diamine

34. Name in anionic complex
Naming Complexes
3. The identity of the central metal ion and its oxidation state
Name changes depending on whether complex is positively or negatively charged.
POSITVELY Charged: Metal has normal name and ox state in brackets
e.g., [Cu(H2O)6]2+ hexaaquacopper(II) ion (Cu in ox state +2)
NEGATIVELY Charged: Ox state still in brackets. Add suffix “-ate” to end of metal
e.g., [CuCl4]2- tetrachlorocuprate(II) ion(Cu in ox state +2)
Metal
Name in anionic complex
Chromium
Chromate
cobalt
Cobaltate
Copper
Cuprate
Iron
Ferrate
Manganese
Manganate
Nickel
Nickelate
Silver
Argenate
Vanadium
Vanadate
Aluminium is not a TM, but included here for completeness

35. Examples [Ag(NH3)2]+ [Co(NH3)6]2+ [Co(H2O)6]2+ [CuCl4]2- [AgCl2]-
Diamminesilver(I)
Hexaamminecobalt(II)
Hexaaquacobalt(II)
Tetrachlorocuprate(II)
Dichloroargenate(I)

36. Naming Complexes
If 2 or more different ligands are present – name in alphabetical order (of the ligand, not the number prefix)
[Cu(H2O)5(OH)2]+
Pentaaquadihydroxocopper(II)
[Cu(H2O)2(NH3)4]2+
Tetraamminediaquacopper(II)

37. Notes on naming ... 1. Oxidation state NOT charge:
The number in brackets in the name is the oxidation state of the central TM ion, NOT the charge on the complex.
[Cu(H2O)6]2+Hexaaquacopper(II)
[CuCl4]2-Tetrachlorocuprate(II)
2. When writing formula, put the central metal ion first, then the ligands:
They are written in alphabetical order of first symbol in their formula (not written names)
E.g., tetraaquadichlorochromium(III)
[CrCl2(H2O)4]+ and not [Cr(H2O)4Cl2]+
3. As An aside ... IUPAC Says When writing formula, write the ligand so that its donor atom symbol is nearest to the central metal ion:
So H2O Should be written as (OH2)
BUT to avoid confusion, we will use H2O A Level textbooks and exam papers use the non-IUPAC Convention, athough technically incorrect

38. Quick Check ... Name the following: [Fe(H2O)6]2+ [Cr(NH3)6]3+
[Ag(CN)2]-
[MnCl4]2-
[Fe(H2O)4(OH)2]+
Write the formula of the following:
Diaquasilver(I)
Hexaaquavanadium(III)
Tetracyanonickelate(II)
Tetrachloroferrate(II)
Diaquatetrahydroxoaluminate(III)

39. Quick Check ... Name the following: [Fe(H2O)6]2+ hexaaquairon(II)
[Cr(NH3)6]3+ hexaamminechromium(III)
[Ag(CN)2]- dicyanoargenate(I)
[MnCl4]2- tetrachloromanganate(II)
[Fe(H2O)4(OH)2]+ tetraaquadihydroxoiron(III)
Write the formula of the following:
Diaquasilver(I) [Ag(H2O)2]+
Hexaaquavanadium(III) [V(H2O)6]3+
Tetracyanonickelate(II) [Ni(CN)4]2-
Tetrachloroferrate(II) [FeCl4]2-
Diaquatetrahydroxoaluminate(III) [Al(H2O)2(OH)4]-

40. Introduction to transition metals
be able to deduce the electronic configurations of atoms and ions of the d-block elements of period 4 (Sc–Zn), given the atomic number and charge (if any)
know that transition metals are d-block elements that form one or more stable ions with incompletely-filled d-orbitals
understand why transition metals show variable oxidation number
know what is meant by the term ‘ligand’
understand that dative (coordinate) bonding is involved in the formation of complex ions
know that a complex ion is a central metal ion surrounded by ligands
understand the meaning of the term ‘coordination number’
understand why H2O, OH− and NH3 act as monodentate ligands
be able to identify bidentate ligands, such as NH2CH2CH2NH2 and multidentate ligands, such as EDTA4−

41. Multidentate Ligands

42. Denticity Denticity – comes from the Latin word ‘dentis’ meaning tooth
Monodentate ligands – think like ‘one tooth’ or ‘one bite’
Ligand only using one pair of electrons on the atom to form the dative bond with the metal ion.
So what would bidentate mean?
What about multidentate?
Be careful!
The coordination number is not defined as the number of ligands in a complex. This is why.

43. Complex Formation [Cu(H2O)6]2+ [CuCl4]2-
“Dentate” – Latin for “tooth” ...
How often they can bite the metal ion
Unidentate ligands – form one co-ordinate bond
e.g. H2O:, :OH-, :NH3, :CN-, :Cl-
[Cu(H2O)6]2+
[CuCl4]2-
Draw out the Lewis structures (dot-and cross diagrams) of the ligands as well
Show each co-ordinate bond as an arrow pointing from the ligand to the central metal ion

44. Complex Formation [Cr(C2O4)3]3- [Cr(en)3]3+
Bidentate ligands – form two co-ordinate bonds
ethanedioate
(C2O42-)
1,2-diaminoethane
(en)
[Cr(C2O4)3]3-
[Cr(en)3]3+
Can donate 2 pairsof e- to the central metal ion in a complex
Common ligands: 1,2-diaminoethane
Ethanedioate ion

45. Complex Formation
Bidentate ligands – form two co-ordinate bonds
1,2-diaminoethane
(en)
How would you show the reaction between hexaaquachromium (III) and 1,2-diaminoethane?
[Cr(en)3]3+
Can donate 2 pairsof e- to the central metal ion in a complex
Common ligands: 1,2-diaminoethane
Ethanedioate ion

46. Complex Formation e.g. [Cu(EDTA)]2-
Multidentate ligands – form several co-ordinate bonds
EDTA4-
e.g. [Cu(EDTA)]2-
EDTA4- can donate 6 pairs of e- to the metal ion.
2 lone pairs are on its N atoms and 4 are on the O on the carboxylate groups.
EDTA can be used (under medical supervision) as antidote to poisoning by TM (usually lead poisoning)
Chelated ions are excreted in urine
My supervisor at St. Andrews fed EDTA to his son who had swallowed some TM compound that was in his house! Think it was lead.

47. Chelation:
Complex ions with polydentate ligands are called “Chelates”
Greek for “Claw”
Chelates can be used to effectively remove d-block metal ions from solution

48. Questions page 103 edexcel workbook Page 103 edexcel revision guide

49. Introduction to transition metals
be able to deduce the electronic configurations of atoms and ions of the d-block elements of period 4 (Sc–Zn), given the atomic number and charge (if any)
know that transition metals are d-block elements that form one or more stable ions with incompletely-filled d-orbitals
understand why transition metals show variable oxidation number
know what is meant by the term ‘ligand’
understand that dative (coordinate) bonding is involved in the formation of complex ions
know that a complex ion is a central metal ion surrounded by ligands
understand the meaning of the term ‘coordination number’
understand why H2O, OH− and NH3 act as monodentate ligands
be able to identify bidentate ligands, such as NH2CH2CH2NH2 and multidentate ligands, such as EDTA4−

50. Introduction to transition metals
be able to deduce the electronic configurations of atoms and ions of the d-block elements of period 4 (Sc–Zn), given the atomic number and charge (if any)
know that transition metals are d-block elements that form one or more stable ions with incompletely-filled d-orbitals
understand why transition metals show variable oxidation number
know what is meant by the term ‘ligand’
understand that dative (coordinate) bonding is involved in the formation of complex ions
know that a complex ion is a central metal ion surrounded by ligands
understand the meaning of the term ‘coordination number’
understand why H2O, OH− and NH3 act as monodentate ligands
be able to identify bidentate ligands, such as NH2CH2CH2NH2 and multidentate ligands, such as EDTA4−