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Transitional Elements

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1 Transitional Elements
PowerPoint Chemistry Transitional Elements

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

3 USES: Transition Metals
Titanium – excellent 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 parts 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 PROPERTIES OF TRANSITION METALS

5 PROPERTIES OF TRANSITION METALS
TRANSITION ELEMENTS: Lie within the d-block elements Titanium  Copper Metals  Conductors of heat & electricity  Shiny, strong & hard  High melting & boiling points Scandium & Zinc are d-block elements but NOT transition elements…you will see why later! Physical properties

6 THE FIRST ROW TRANSITION ELEMENTS
Properties strong metallic bonds due to small ionic size and close packing higher melting, boiling points s-block metals. Many are COLOURED. Ca Sc Ti V Cr Mn Fe Co m. pt / °C density / g cm 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

7 PROPERTIES OF TRANSITION METALS
GENERAL PROPERTIES The general properties of transition metals are: they form complexes they form coloured ions they form variable oxidation states they have catalytic activity Chemical properties

8 ELECTRONIC STRUCTURE All characteristic properties are a result of their electronic structure The transition metals have a partially filled 3d energy sub level in their atoms or ions In general there are two outer 4s electrons, and electrons are added to the inner 3d sub level Check Point 1 What are the full electronic configurations of the elements in the first d-block row? Be careful with Cr and Cu!!! Extension: Draw box and arrow for 3d and 4s shells

9 FORMING IONS V [Ar] 3d34s2 V3+
In all ions of d-block elements, the 3d subshell is lower in energy than the 4s subshell So the 4s electrons are always removed first 3d electrons are only removed after all 4s electrons have been removed To write the electronic structure for Co2+: Co [Ar] 3d74s2 Co2+ [Ar] 3d7 The 2+ ion is formed by the loss of the two 4s electrons. To write the electronic structure for V3+: V [Ar] 3d34s2 V3+ [Ar] 3d2

10 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) NB: ∵ = ‘therefore’ 10

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
Transition elements have similar atomic radii which make them possible for the atom of one element to replace those of another element in the formation of alloy e.g. Mn is for conferring hardness and wearing resistance to its alloy (duralumin) Cr is for conferring inertness on stainless steel 12

13 General Features Transition Metals
Iron is used to make ships Ramstore Bridge (Astana) - constructed using steel 13

14 General Features Transition Metals
Tungsten in a light bulb The statue is made of alloy of copper and zinc Titanium is used in making aircraft Jewellery made of gold 14

15 General Features Transition Metals
Variations in atomic and ionic radii of the first series of d-block elements 15

16 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 16

17 General Features Transition Metals
The atomic size increases at the end of the series ∵ the screening and repulsive effects of the 3d electrons reach a maximum The reasons for the trend of the ionic radii of the d-block elements are similar to those for the atomic radii. Remember that the electrons have to be removed from the 4s orbital first 17

18 Variable oxidation state
Observations: 1. Sc and Zn do not exhibit variable oxidation states. Sc3+ has electronic configuration of argon (i.e. 1s22s22p63s23p6). Zn2+ has the electronic configuration of [Ar] 3d10. Other oxidation states are not possible. 2. Except Sc, all elements have +2 oxidation state. Except Zn, all elements have +3 oxidation state 3. The highest oxidation state is +7 at Mn. This corresponds to removal of all 3d & 4s electrons. (Note: max.oxidation state is NEVER greater than the total number of 3d & 4s electrons) 18

19 Variable oxidation state
4. There is a reduction in the number of oxidation states after Mn. ∵ decrease in the number of unpaired electrons and increase in nuclear charge which holds the 3d electrons more firmly 5. 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) 19

20 The Reactions and their Colours Do you recall
The Reactions and their Colours Do you recall? Now you will see why these colours exist Metal Aqueous ion NaOH goes Neutral ppt NaOH excess NH3(aq) SAME AS NaOH base Excess Na2CO3(aq) Weak Base ppts are Neutral Fe (II) Green [Fe(H2O)6]2+(aq) GREEN ppt Fe(H2O)4(OH)2(s) No change Green ppt FeCO3(s) 2+ not able to be acid (III) Yellowish [Fe(H2O)6]3+(aq) Brown ppt Fe(H2O)3(OH)3(s) Acid Base Rx Bubbles of CO 2(g) Cu Blue [Cu(H2O)6]2+(aq) BLUE ppt Cu(H2O)4(OH)2(s) DEEP BLUE [Cu(H2O)2(NH3)4]2+(aq) Blue-Green ppt CuCO3(s) Al [Al(H2O)6]3+(aq) WHITE ppt Al(H2O)3(OH)3(s) [Al(OH)4]–(aq) Colorless Bubbles of CO2(g)

21 Formulas of Coordination Compounds
Rules for writing formulas: 1. The cation is written first 2. In the complex ion, neutral ligands are written before anionic ligands, and the formula for the whole ion is placed in brackets. 3. Ligands are named, in alphabetical order, before the metal ion. If the complex ion is an anion the metal name must end with –ate and with Latin names (see table) where possible

22 Nomenclature of Complexes
Complexes are named according to the rules recommended by IUPAC The rules of naming a complex are as follow: 1. (a) For any ionic compound, the cation is named before the anion. (b) If the compound is neutral, then the name of the complex is name of the compound (c) In naming a complex, the ligands are named before the central metal atom or ion, negative ones first and then neutral ones 22

23 Nomenclature of Complexes
(d) The number of each type of ligands are specified by the Greek prefixes: mono-, di-, tri-, tetra-, penta-, hexa-, etc. (e) 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 [ ] 23

24 Nomenclature of Complexes
2. (a) The root names of anionic ligands always end in -o. e.g. CN– cyano Cl– chloro (b) The names of neutral ligands are the names of the molecules, except NH3, H2O, CO and NO e.g. NH3 ammine H2O aqua Anionic ligand Name of ligand Neutral ligand Bromide (Br–) Chloride (Cl–) Cyanide (CN–) Fluoride (F–) Hydroxide (OH–) Sulphate(VI) (SO42–) Amide (NH2–) Bromo Chloro Cyano Fluoro Hydroxo Sulphato Amido Ammonia (NH3) Water (H2O) Carbon monoxide (CO) Nitric oxide (NO) Ammine Aqua Cabonyl Nitrosyl 24

25 Nomenclature of Complexes
3. (a) If the complex is anionic, then the suffix -ate is attached to the name of the metal, followed by the oxidation state of that metal e.g. K2CoCl4 potassium tetrachlorocobaltate(II) K3Fe(CN)6 potassium hexacyanoferrate(III) [CuCl4]2– tetrachlorocuprate(II) ion 25

26 Name in anionic complex
Nomenclature of Complexes Metal Name in anionic complex Titanium Chromium Manganese Iron Cobalt Nickel Copper Zinc Platinum Titanate Chromate Manganate Ferrate Cobaltate Nickelate Cuprate Zincate Platinate (b) If the complex is cationic or neutral, then the name of the metal is unchanged. e.g. [CrCl2(H2O)4]+ dichlorotetraaquachromium(III) ion [CoCl3(NH3)3] trichlorotriamminecobalt(III) 26

27 Nomenclature of Complexes
Examples: 1. Ionic complexes 27

28 Nomenclature of Complexes
2. Neutral complex 28

29 COMPLEX FORMATION Check Point 5
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] OS: +2 CN:4 [Fe(CN)6] OS: +3 CN:6

30 sodium hexafluoroaluminate
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

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

32 Exercise (a) [Co(H2O)6]Br3 (b) Na2[PtCl4]
Name the following coordination compounds. (a) [Co(H2O)6]Br3 (b) Na2[PtCl4] a) hexaaquacobalt(III) bromide b) sodiumtetrachloro-platinate(II) (a) Hexaaquacobalt(III) bromide (b) Sodium tetrachloroplatinate(II) (ate because it is a anion)

33 Try a few Ends with ate as is an anion [CuCl4]2- [Cu(H2O)6]2+
Complex Ion Name Cr[Cl4(OH2)2]- Ends with ate as is an anion diaquatetrachlorochromate (III) io [Cr(OH2)(NH3)5]3+ pentaammineaquachromium (III) ion [Al(OH)Cl3]- trichlorohydroxoaluminate (III) ion [CrCl2(OH2)4]+ tetraaquadichlorochromium (III) ion Formula Name [CuCl4]2- tetrachlorochromium (II) ion Formula Name [Cu(H2O)6]2+ Hexaaquacopper(II) ion

34 ELECTRONIC CONFIGURATIONS (and some Ions)
Note: Removing e- from the highest level of n FIRST(or largest number) Sc 1s2 2s2 2p6 3s2 3p6 4s2 3d1 Ti 1s2 2s2 2p6 3s2 3p6 4s2 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 Sc3+ 1s2 2s2 2p6 3s2 3p6 4s2 3d1 Ti s2 2s2 2p6 3s2 3p6 4s2 3d2 Ti s22s2p63s23p6 4s2 3d2 goes to 3d1 Ti s2 2s2 2p6 3s2 3p6 Mn can have 7 ions An exception Cu. 1s2 2s2 2p6 3s2 3p6 3d10 4s1 Cu+ 1s2 2s2 2p6 3s2 3p6 3d10 Cu2+ 1s2 2s2 2p6 3s2 3p6 3d9 Zn s2 2s2 2p6 3s2 3p6 4s2 3d10

35 Finding the Number of Unpaired Electrons
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)? 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 6s 4f There are 6 unpaired e− in Sm., the more UNPAIRED electrons, the more magnetic

36 Concept Check What is the expected electron configuration of Sc+? Explain. [Ar]3d2 Normally Sc electronic config = 1s2 2s2 2p6 3s2 3p6 4s2 3d1 To create an ion you take way from the highest level of n. The electron configuration for Sc+ is [Ar]3d2. The 3d orbitals are lower in energy than the 4s orbitals for ions. Students need to know this when they draw energy level diagrams using the Crystal Field model.

37 CHROMIUM AN EXCEPTION 1s2 2s2 2p6 3s2 3p6 4s1 3d5
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS CHROMIUM AN EXCEPTION 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s1 3d5 One would expect the configuration of chromium atoms to end in 4s2 3d4. 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. Half filled d orbitals are more stable

38 Cations are positive (“pussy-tive) ions
COMPLEX FORMATION COMPLEXES Complexes are formed when transition metals or their ions form co-ordinate (dative) bonds with ligands A complex ion is an ion comprising of one or more ligands attached to a central metal cation by means of a dative covalent bond Cations are positive (“pussy-tive) ions

39 COMPLEX FORMATION LIGANDS
A ligand is a species which can use its lone pair of electrons on one of its atoms to form a dative covalent bond with a transition metal Examples of ligands are: H2O NH3 Cl- OH- CN-

40 COMPLEX FORMATION CO-ORDINATE BOND
A co-ordinate bond (dative covalent bond) is a covalent bond in which both electrons come from the same atom In the case of complex ions, the co-ordinate bonds are formed by the overlap of an orbital containing a lone pair of electrons with a vacant orbital on the transition metal

41 COMPLEX FORMATION CO-ORDINATION NUMBER
The number of lone pairs of electrons which a cation can accept is known as the coordination number of the cation It depends on the size and electronic configuration of that cation, and also on the size and charge of the ligand Coordination number 6 is the most common, although 4 and 2 are also known

42 COMPLEX FORMATION LEWIS ACID / BASE In complexes:
The metal ion acts as a Lewis Acid Accepts lone pairs of electrons The ligand acts as a Lewis Base Donates lone pairs of electrons Lewis Acid  electron pair acceptor Lewis Base  electron pair donor

43 COMPLEX FORMATION EXAMPLE An example of a complex ion is: [Cu(H2O)6]2+
Note that the formula of the ion is always written inside square brackets The overall charge is written outside the brackets H2O Cu2+ OH2

44 COMPLEX FORMATION MONODENTATE LIGANDS/UNIDENTATE
Meaning ‘single toothed’  form 1 co-ordinate bond Common unidentate ligands are H2O, Cl-, NH3 and CN- Can be negatively charged ions or neutral molecules Ammonia only has 1 pair of electrons to donate Water has 2 lone pairs. BUT they are so close together it can only form one coordinate bond at a time!

45 2 amine groups. Each has a lone pair of electrons to donate
COMPLEX FORMATION BIDENTATE LIGANDS Ligands that can form two co-ordinate bonds since they donate two lone pairs of electrons (from two donor atoms) Examples: Ethane-1,2-diamine (NH2CH2CH2NH2) Each ethane-1,2-diamine molecule forms 2 coordinate bonds with the metal ion 2 amine groups. Each has a lone pair of electrons to donate

46 COMPLEX FORMATION MULTIDENTATE LIGANDS
Can form three or more co-ordinate bonds by donating at least three lone pairs of electrons to the metal ion Extremely stable since the reaction results in an increase in entropy EDTA is a common example How many coordinate bonds can it form? Ethylenediaminetetracetate

47 COMPLEX FORMATION EDTA4- has six lone pairs (two on nitrogen atoms and 4 on oxygen atoms) It can form six coordinate bonds with a metal ion Complex ions with multidentate ligands are called chelates (‘key-lates) from the Greek word for claw

48 COPPER AN EXCEPTION 1s2 2s2 2p6 3s2 3p6 4s1 3d10
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS COPPER AN EXCEPTION 4 4p 4d 4f INCREASING ENERGY / DISTANCE FROM NUCLEUS 3d 4s 3 3p 1s2 2s2 2p6 3s2 3p6 4s1 3d10 One would expect the configuration of copper atoms to end in 4s2 3d9. To achieve a more stable arrangement of lower energy, one of the 4s electrons is promoted into the 3d to make it fully filled.

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

50 Bidentate ligands – form two co-ordinate bonds
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

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

52 Ligands possess one or more lone pair of electrons
SUMMARY LIGANDS Ligands possess one or more lone pair of electrons Thus they are Lewis Bases chloro Cl- amine NH3  unidentate cyano CN- aqua H2O hydroxo OH- oxalate (ox) C2O42- bidentate ethylenediaminetetraacetato  (EDTA) (COOH)2N(CH)2N(COOH)2 hexadentate 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 H2NCH2CH2NH C2O42-

53 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

54 COMPLEX FORMATION Multidentate ligands – form several co-ordinate bonds Actual porphyrin Eg. haem haemoglobin

55 CO-ORDINATION NUMBER & SHAPE
The shape of a complex is governed by the number of ligands or DATIVE BONDS around the central ion Co-ordination No. Shape Example(s) 6 Octahedral [Cu(H2O)6]2+ 4 Tetrahedral [CuCl4]2- 4 Square planar Pt(NH3)2Cl2 2 Linear [Ag(NH3)2]+

56 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+

57 SHAPES OF COMPLEX IONS Co-ordination number 2 4 6 Shape linear
tetrahedral square planar octahedral Bond angles 180º 109½º 90º Occurrence Ag+ complexes Large ligands (e.g. Cl-) Pt2+ complexes Commonest e.g. [Ag(NH3)2]+ [CuCl4]2- [PtCl4]2- [Cu(H2O)6]2+

58 STEREOISOMERISM IN COMPLEXES
E-Z Isomerism e.g. [PtCl2(NH3)2] cis trans

59 CIS-PLATIN Very effective drug to fight cancer (e.g. testicular)
Binds to guanine in DNA and stops replication

60 STEREOISOMERISM IN COMPLEXES
E-Z Isomerism e.g. [CoCl2(NH3)4]+


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