TRANSITION METALS.

TRANSITION METALS

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 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

FIRST ROW TRANSITION ELEMENTS
Physical strong metallic bonds due to small ionic size and close packing Properties 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

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)

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

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

PROPERTIES OF TRANSITION METALS
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

FORMING IONS V [Ar] 3d34s2 V3+ 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

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

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

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

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

Iron is used to make ships Ramstore Bridge (Astana) - constructed using steel 14

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) 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) Ammine Aqua Cabonyl

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

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 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)

Examples: 1. Ionic complexes

2. Neutral complex

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] OS: +2 CN:4 [Fe(CN)6] OS: +3 CN:6

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

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

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

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

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+

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

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

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)

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

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+

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-

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

TRANSITION METALS Explaining colour
Using the key words: Absorbed, transmitted and reflected explain the colours in each of the following:

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

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.

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

Cr3+ (aq) absorbs yellow light and so is violet
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

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

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

RBG [Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

RBG BG [Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

RBG RBG BG [Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

RBG RBG BG B [Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

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

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

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

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 Split

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 Split

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. Split

Recap colour of complexes
3) the changes in the? Hint e.g. [CuCl4]2- yellow Cu(II)to [CuCl4]3-which is Colourless Cu(I) Oxidation number Split

Recap colour of complexes
3) the changes in the Oxidation number But also changing the oxidation state e.g. Fe (II) to Fe (III) can change the colour Since the electrostatic repulsion even with the same ligands is different Split

Example question

Elemental Chromium; 0

CrCl3 (aq); +3 K2CrO4 (yellow) and K2Cr2O7 (orange/red) Both +6

Hydrated chromium(III) chloride, CrCl3.6H2O; +3
[Cr(H2O)6]3+ [Cr(H2O)5Cl]2+ Cr(H2O)4Cl2]+ These 3 are isomers!

Summary Chromium +3 – can be violet or green
+6 – can be red/orange or yellow

TRANSITION METAL COMPLEXES Learning objectives
recognise various acid-base theories and understand the conditions in which each may be used, their strengths and limitations; recognise and know the structure of metal-aqua ions; understand the acid behaviour of these ions and their reactions with ammonia solution, hydroxide and carbonate solutions to produce insoluble hydroxides and complex ions.

Chemsheets AS006 (Electron arrangement)
07/04/2019 CATALYSIS 1 minute chem channel Ethanol to ethene with Al2O3

CATALYSTS - lower Ea Catalysts work by providing…
“AN ALTERNATIVE REACTION PATHWAY WHICH HAS A LOWER ACTIVATION ENERGY” WITHOUT A CATALYST WITH A CATALYST A GREATER PROPORTION OF PARTICLES WILL HAVE ENERGIES IN EXCESS OF THE MINIMUM REQUIRED SO MORE WILL REACT

Heterogeneous Catalysis
3min Heterogeneous Catalysis Catalysts are in a different phases, the surface of a solid and the gas which adsorbs onto the surface forming weak bonds with metal atoms. There are 3 stages... Adsorption Dissimilar surfaces cling together. Incoming a gas lands on an active site (a solid), often a transitional metal. Ex. (Pt) Reaction Adsorbed gases are held in just the right orientation for a reaction to occur. This increases the chances of favourable collisions taking place (satisfying both tenants (parts) of the Collision Theory. Desorption products are then released from the metal

HETEROGENEOUS CATALYSTS
Example reaction – V2O5 in Contact Process. Which is catalyst and which is reaction intermediate? Step 1: V2O5 + SO2  V2O4 + SO Fast Step 2 : V2O4 + ½ O2  V2O5 Slow Overall: SO2 + ½ O2  SO3

ANIMATION

1) Reactants adsorbed onto surface (onto active sites). W weakens bonds brings molecules closer more favourable orientation 2) Reaction takes place. 3) Products are desorbed (leave the surface). Too strong (e.g. W) Reactants cannot move round surface and products cannot desorb. Too weak (e.g. Ag) Reactants not adsorbed. Ideal (e.g. Ni, Pt)

Chem Channel (1min) Nature of catalyst Large surface area. Spread thinly over ceramic honeycomb. Catalytic Poisons : Some substances may block active sites (i.e. they adsorb and will not come off). Can ruin catalyst. e.g. Pb in catalytic converters

HOMOGENEOUS CATALYSTS
Transition metal catalyst works by metal varying oxidation state Mn2+ e.g. 2 MnO H+ + 5 C2O42- → 2 Mn H2O + 10 CO2 the reaction is catalysed by one of the products (Mn2+) so is autocatalysis

Metal-Aqua Ions the 3 L’s or L3
igands one pair ewis Base Most of these complexes have an octahedral shape with a co-ordination number of 6 L.O.: recognise and know the structure of metal-aqua ions

CuSO4 + 6H2O → [Cu(H2O)6]2+ + SO42-
Anhydrous white copper(II) sulfate dissolves in water to produce blue hexaaquacopper(II) CuSO4 + 6H2O → [Cu(H2O)6]2+ + SO42- White solid Blue

CoCl2 + 6H2O → [Co(H2O)6]2+ + 2Cl-
Blue anhydrous cobalt(II) chloride dissolves in water to produce pink hexaaquacobalt(II) CoCl2 + 6H2O → [Co(H2O)6]2+ + 2Cl- Blue solid Pink

FeSO4 + 6H2O → [Fe(H2O)6]2+ + SO42-
Pale green iron(II) sulfate dissolves in water to produce pale green hexaaquairon(II) FeSO4 + 6H2O → [Fe(H2O)6]2+ + SO42- Pale green solid Pale green

THE AQUEOUS CHEMISTRY OF IONS
Water acts as a Lewis Base – a lone pair donor and forms a co-ordinate bond to the metal ion (a Lewis Acid) Na+ Less Acidic Al3+ More

Bronsted – Lowry Acid Base Reactions 2+ vs 3+ M3+ ions [M(H2O)6]3+(aq) H2O(l) [M(H2O)3(OH)3] (aq) H3O+(aq) M2+ ions [M(H2O)6]2+ (aq) H2O(l) [M(H2O)5(OH)]+(aq) H3O+(aq) Stronger bases (e.g. CO32- , NH3 and OH¯ ) can remove further protons A-B Practice Question write out the reactions involved when a copper-aqua 2+ ion reacts with ammonia [Cu(H2O)6]2+(aq) NH3(aq)  [Cu(OH)2(H2O)4](s) NH4+(aq)

Carbonates Metal 3+ (M 3+ ) reactions: 2[M(H2O)6] CO32-  2[M(H2O)3(OH)3] (s) + 3CO2 + 3H2O What reaction type is this Metal 2+ (M 2+ ) reactions: [M(H2O)6] 2+ + CO32-  MCO3 (s) + 6H2O A-B Ppt

Exam questions Q1 Why do separate solutions of iron(II) sulfate and iron(III) sulfates have different pH values? [2 marks] Q2 a) Write an ionic equation to show the formation of precipitate when sodium carbonate is added to aqueous iron (II) sulfate. [1 mark] b)Explain how sodium carbonate reacts with aqueous iron (III) chloride to form a precipitate. Include equations

GREEN PEN Fe3+ has a higher charge density, thus H2O is more polarized and more easily donates H+ ions in a Bronsted – Lowry fashion a) [Fe(H2O)6]2+(aq) + CO32-(aq)  FeCO3(s) H2O 2.b) 2[Fe(H2O)6]3+(aq) + 3CO32-(aq)  2[Fe(OH)3(H2O)3](s) + 3H2O(l) + 3CO2(g) rusty-brown ppt.

Cobalt (II) REACTIONS All reactions are sensible except:
NH3 Excess Exceptions Co2+, Cr3+ with 6NH3 and Cu 2+, with just 2NH3 Excess exception OH- Al 3+ with 1 OH- Cobalt (II)

COBALT(II) OH¯ [Co(H2O)6]2+(aq) OH¯(aq)  [Co(OH)2(H2O)4](s) H2O(l) PINK PINK ppt. A-B NH3 [Co(H2O)6]2+(aq) NH3(aq)  [Co(OH)2(H2O)4](s) + 2NH4+(aq) PINK PINK ppt. Excess NH3 [Co(OH)2(H2O)4](s) + 6NH3(aq)  [Co(NH3)6]2+(aq) + 4H2O(l) + 2OH¯(aq) PINK PINK ppt. OR instead of 2 steps above write it Excess NH3 in 1 step as: [Co(H2O)6]2+(aq) NH3(aq)  [Co(NH3)6]2+(aq) + 6H2O(l) CO32- [Co(H2O)6]2+(aq) CO32-(aq)  CoCO3(s) H2O(l) PINK mauve ppt. Cl- [Co(H2O)6]2+(aq) Cl¯(aq)  [CoCl4]2- (aq) H2O(l) PINK Blue, TERAHEDRAL , Coordination #4 A-B LS Ppt LS

CHROMIUM(III)

REACTIONS OF CHROMIUM(III)
OH¯ [Cr(H2O)6]3+(aq) OH¯(aq)  [Cr(OH)3(H2O)3](s) H2O(l) violet, octahedral green ppt Amphoterism The 3+ ion forms an Amphoteric Precipitate [Cr(OH)3(H2O)3](s) [Cr(OH)3(H2O)3](s) H3O+(aq)  [Cr(H2O)6]3+(aq) H2O(l) [Cr(OH)3(H2O)3](s) OH¯(aq)  [Cr(OH)6]3-(aq) H2O(l) green ppt green, octahedral NH3 [Cr(H2O)6]3+(aq) NH3(aq)  [Cr(OH)3(H2O)3](s) + 3NH4+(aq) violet, octahedral green ppt Excess NH3 [Cr(OH)3(H2O)3](s) + 6NH3(aq)  [Cr(NH3)6]3+(aq) + 3H2O(l) + 3OH¯(aq) green ppt Red brown OR instead of 2 steps above write it Excess NH3 in 1 step as: [Cr(H2O)6]2+(aq) NH3(aq)  [Cr(NH3)6]2+(aq) + 6H2O(l) CO32- 2 [Cr(H2O)6]3+(aq) + 3CO32-(aq)  2[Cr(OH)3(H2O)3](s) + 3H2O(l) + 3CO2(g) violet, octahedral green, octahedral A-B A-B A-B A-B LS A-B

OXIDATION REACTIONS OF CHROMIUM(VI)
Being in the highest oxidation state (+6), chromium(VI) will be a GOOD oxidising agent. Dichromate is widely used in both organic (oxidation of alcohols) It can also be used as a volumetric reagent (titration) as well Cr2O72-(aq)  2Cr3+(aq) orange green Its E° value is lower than that of Cl2 (1.36V) so can be used in the presence of Cl¯ ions

Copper (II)

REACTIONS OF COPPER(II)
OH¯ [Cu(H2O)6]2+(aq) OH¯ (aq)  [Cu(OH)2(H2O)4] (s) + 2H2O(l) blue, octahedral pale blue ppt. octahedral Look at the products, how can you tell this is an acid base reaction? NH3 [Cu(H2O)6]2+(aq) NH3(aq)  [Cu(OH)2(H2O)4] (s) + 2NH4+ (aq) blue, octahedral blue, octahedral Excess NH3 [Cu(OH)2(H2O)4](s) + 4NH3(aq)  [Cu(NH3)4(H2O)2]2+(aq) + 2H2O (l) + 2OH¯(aq) blue, octahedral Royal DEEP blue CO32- [Cu(H2O)6]2+(aq) CO32- (aq)  CuCO3(s) H2O (l) blue, octahedral blue ppt. Cl¯ [Cu(H2O)6]2+(aq) + 4Cl¯ (aq)  [CuCl4]2-(aq) H2O (l) blue, octahedral yellow, tetrahedral A-B A-B LS Ppt LS

Manganese (II)

REACTIONS OF MANGANESE(II)
OH¯ [Mn(H2O)6]2+(aq) OH¯(aq)  [Mn(OH)2(H2O)4](s) H2O(l) pale pink, octahedral off-white ppt. NH3 [Mn(H2O)6]2+(aq) + 2NH3(aq)  [Mn(OH)2(H2O)4](s) + 2NH4+(aq) pale pink, octahedral off-white ppt. CO32- [Mn(H2O)6]2+(aq) CO32-(aq)  MnCO3(s) H2O(l) Cl¯ [Mn(H2O)6]2+(aq) + 4Cl¯(aq)  [MnCl4]2-(aq) H2O(l) pale pink, octahedral tetrahedral A-B A-B Ppt LS

VOLUMETRIC USE OF MANGANATE(VII)
Potassium manganate(VII) in (H2SO4) is useful for carrying out redox volumetric analysis. MnO4¯(aq)  Mn2+(aq) MnO4¯ is powerful enough to oxidise the chloride ions in hydrochloric acid fumes No indicator is required; the end point being the first sign of a permanent pale pink colour. Iron(II) MnO4¯(aq) H+(aq) + 5Fe2+(aq)  Mn2+(aq) Fe3+(aq) + 4H2O(l) this means that moles of Fe = 5 moles of MnO4¯

Iron (II)

REACTIONS OF IRON(II) OH¯
[Fe(H2O)6]2+(aq) OH¯(aq)  [Fe(OH)2(H2O)4](s) H2O(l) pale green dirty green ppt. it slowly turns a rusty brown colour due to oxidation by air to iron(III) Fe(OH)2(s) + OH¯(aq)  Fe(OH)3(s) e¯ dirty green ppt. rusty brown NH3 [Fe(H2O)6]2+(aq) NH3(aq)  [Fe(OH)2(H2O)4](s) NH+4 (aq) pale green dirty green ppt. CO32- [Fe(H2O)6]2+ (aq) + CO32-(aq)  FeCO3(s) H2O pale green Off-white A-B OX A-B Ppt

Iron (III)

IRON(III) OH¯ [Fe(H2O)6]3+(aq) OH¯(aq)  [Fe(OH)3(H2O)3](s) H2O(l) yellow rusty-brown ppt. CO32- 2[Fe(H2O)6]3+(aq) + 3CO32-(aq)  2[Fe(OH)3(H2O)3](s) H2O(l) + 3CO2(g) yellow rusty-brown ppt. NH3 [Fe(H2O)6]3+(aq) NH3(aq)  [Fe(OH)3(H2O)3](s) NH4+(aq) yellow rusty-brown ppt SCN¯ [Fe(H2O)6]3+(aq) SCN¯(aq)  [Fe(SCN)(H2O)5]2+(aq) + H2O(l) yellow blood-red colour Very sensitive; BLOOD RED COLOUR confirms Fe(III). No reaction with Fe(II) A-B A-B A-B LS

Silver (I)

REACTIONS OF SILVER(I)
eg AgCl(s) NH3(aq)  [Ag(NH3)2]+(aq) Cl¯(aq) [Ag(NH3)2] Used in Tollen’s reagent (SILVER MIRROR TEST) Tollen’s reagent is used to differentiate between aldehydes and ketones.

Aluminum (III)

REACTIONS OF ALUMINIUM
Aluminium is not a transition metal as it doesn’t use of d orbitals and is COLOURLESS OH¯ [Al(H2O)6]3+(aq) OH¯(aq)  [Al(OH)3(H2O)3](s) H2O(l) colourless, octahedral white ppt. Excess OH¯ [Al(OH)3(H2O)3](s) + 1 OH¯(aq)  [Al(OH)4(H2O)3]-(aq) + HOH (l) white ppt. colourless, octahedral Amphoterism The 3+ ion forms an Amphoteric Precipitate [Al(OH)3(H2O)3](s) [Al(OH)3(H2O)3] (s) H+ (aq)  [Al(H2O)6]3+(aq) [Al(OH)3(H2O)3] (s) OH¯(aq)  [Al(OH)4(H2O)2]-(aq) + H2O(l) Or [Al(OH)3(H2O)3] (s) OH¯(aq)  [Al(OH)6]3-(aq) H2O(l) NH3 [Al(H2O)6]3+(aq) NH3(aq)  [Al(OH)3(H2O)3] (s) NH4+(aq) CO32- 2 [Al(H2O)6]3+(aq) CO32-(aq)  2[Al(OH)3(H2O)3] (s) H2O(l) + 3CO2(g) A-B A-B A-B A-B A-B

Summary All reactions are sensible except: NH3 Excess Exceptions
Co2+, Cr3+ with 6NH3 and Cu 2+, with just 2NH3 Excess exception OH- Al 3+ with 1 OH-

Chirality: absent symmetry
If a molecule has a plane of symmetry it is chiral and Enantiomers are possible Plane of symmetry Achiral (one structure) Rearranged there is no plane of symmetry Chiral (two enantiomer)

Some coordination complexes with mixed bidentate ligands have optical isomers and are said to be chiral.

Chelates Monodentate = 1 tooth (bond) Bidentate = 2 teeth (bonds)
H2O, OH-, NH3, CN-, SCN-, Cl- Bidentate = 2 teeth (bonds) Chelate = claw Ethylenediamine oxalate Polydentate (Many teeth) EDTA = ethylenediaminetetraacetate Very stable complexes Used to scavenge toxic metals

Chelate Effect If a multidentate ligand (such as EDTA4-) replaces a unidentate one(such as water) there is a thermodynamic ∆G advantage, even if there is little difference in bond strength ∆H. 1 M(H2O)62+ + 1 EDTA  1 M(EDTA)2- + 6 H2O 2 species species Even if we assume that there is little change in the bond energy there is a large increase in entropy ∆S, so the ∆G would be negative. ∆G = ∆H - T∆S

Exam questions

GREEN PEN

TRANSITION METALS.

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TRANSITION METALS.

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