Download 15. The Transition Metals

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What are the transition elements?
The transition elements are d-block elements which
form one or more stable ions with incomplete d subshell electrons.
group 2
group 3
 A transition element forms at least one ion with a
partially-filled d-subshell
Sc Ti V Cr Mn Fe Co Ni Cu Zn
Y Zr Nb Mo Tc Ru Rh Pd Ag Cd
La Hf Ta W Re Os Ir Pt Au Hg
Here, the word
‘transition’ is
used to mean
‘in-between’.
Ac Rf Db Sg Bh Hs Mt Ds Rg ?
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Uses of coloured trans. metal compounds
The coloured compounds of transition
metals can also be used in many
ways, for example:
 to colour stained glass windows
 to colour paints
 as coloured glazes on pottery.
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What are the uses of the transition metals?
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Catalysis
• Catalysis plays an essential aspect in
about 90% of all chemical manufacturing.
• Ni and Pt are very heterogeneous
catalysts.
• Pt, Rh, and Pd are used in catalytic
converters.
• V2O5 is used in conversion of SO2 to SO3.
• Polyethylene is formed catalytically.
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General Chemistry:
Chapter 24
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First row d-block elements
Elements
Atomic num.
Sc
21
Ti
V
Cr
Mn
22
23
24
25
Fe
Co
Ni
26
27
28
Cu
Zn
29
30
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Electronic Configuration
[Ar] …
[Ar] 3d1 4s2
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Most common oxidation state
Elements
Sc
Electronic
Configuration
[Ar] 3d1 4s2
Known oxidation
state
+3
Ti
V
Cr
Mn
[Ar] 3d2 4s2
[Ar] 3d3 4s2
[Ar] 3d5 4s1
[Ar]3d5 4s2
+3, +4
+2, +3, +4, +5
+3, +6
+2, +4, +6, +7
Fe
Co
Ni
[Ar] 3d6 4s2
[Ar] 3d7 4s2
[Ar] 3d8 4s2
+2, +3
+2, +3
+2
Cu
Zn
[Ar] 3d10 4s1
[Ar] 3d10 4s2
+1, +2
+2
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Write the electron configuration of
3+
•Cr
2+
•Cu
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exercise
• Explain why scandium (III) and zinc (II)
cations are not called transition elements.
• Why is the maximum oxidation state of
manganese +7?
• In the higher oxidation states, the
elements exist as covalently bonded oxocompounds rather than atomic ions.
Explain this phenomenon
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Characteristic of transitional metals
on their compounds
• Variable oxidation state
Due to similar energy of 4s and 3d
• Formation of coloured ions / complex ions
Due to electrons transition between d-orbitals
• Catalytic activity
Provide alternative reaction mechanism with
lower activation energy
• Paramagnetism
Unpaired or odd electrons
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What are the properties of the transition metals?
The transition metals are known as ‘typical’ metals because
of their physical properties. They are:
 lustrous (bright and shiny).
 hard and strong.
 high density.
 malleable (can be bent and pressed into different
shapes) and ductile (can be drawn into wires).
 good conductors of heat and electricity.
 high melting and boiling points (except mercury,
which is liquid at room temperature).
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Color and Magnetism
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General Chemistry:
Chapter 24
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Comparing properties of different metals
How do the properties of transition metals compare with
those of alkali metals?
Compared to the alkali metals, the transition metals:
 are harder and stronger. They cannot be cut with a knife.
 are more dense. This means that in a fixed volume of
metal there are more atoms of a transition metal than
there are of an alkali metal.
 have higher melting and boiling points – except mercury.
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Comparing densities of metals
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Comparing melting points of metals
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True or false?
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Redox reactions
• A positive Ecell indicates a
thermodynamically feasible reaction
• A negative Ecell indicates a
thermodynamically non-feasible reaction
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• Judging from Ecell [ data booklet ]
o Predict the outcome of mixing aqueous
iron(II) with chlorine.
o Predict the outcome of mixing acidified
tin (II) with hydrogen peroxide (H2O2)
o Which one is the better oxidising agent
in acidified solution : KMnO4 or K2Cr2O7
to oxidized solution of iron(II)
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Complex ions
• A compound in which ligand molecules
form (dative) co-ordinate bonds to a centre
metal atom or ion.
• Ligand :a ion or molecule that has at least
a lone pair of electrons available for
donation to the central metal atom or ion.
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How to write a complex structure
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Features of complex ions
• Net charge on complex ions
Net
charge
Oxidation
number
Knowing the charge on a complex ion and the
charge on each ligand, one can determine the
oxidation number for the metal.
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Features of complex ions
• In a compound, complex ion attaches to a
counter ion.
K4[Fe(CN)6]
Na2CuCl4
[Cu(NH3)4]SO4
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Features of complex ions
• Co-ordination number
(number of dative bonds attached)
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Ligands
• Neutral
H2O, NH3, CO, amines, etc
• Ionic
Cl-, CN-, etc
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Types of ligands
• Based on number of dative bonds:
o Monodentate [ one dative bond ]
o H2O, NH3, halide, CN-, CO
o Bidentate [ two dative bonds ]
o Ethylenediamine, oxalate ions
o Polydentate [ more than two dative bonds ]
o EDTA (EthyleneDiamineTetraAcetate ion)
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chelate
• Bidentate or polydentate ligands that form
ring in a complex ion.
– Ethane-1,2-diamine [“en”]
– Ethanedioate ions [“ox”]
– EDTA
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Rule for naming complex ions
• Complex cation
– Names of ligands are given first, then the
central ion with its oxidation state in brakets
– Ligands are named in alphabetical order with
suitable prefix to indicate number of ligand
present [di, tri, tetra, etc]
– The ligand and central ion are named without
space
• Complex anion
– Similar method, except central metal ion is
altered to end in -ate
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Ligands
H2O NH3
Name
aqua
F-
ammine fluoro
Cl-
CN- SCN-
OH-
chloro
cyano thiocyanate Hydroxo
These are strong ligands
Cationic complexes Anionic complexes
Titanium
Titanate
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vanadium
Manganese
Iron
Vanadate
Manganate
Ferrate
Copper
Cuprate
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Table 25.2 Some Common Monodentate
Ligands.
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General Chemistry:
Chapter 25
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Give names
•
•
•
•
•
•
Cu(en)22+
Fe(Ox)33[Cu(H2O)6]2+
[Cr(NH3)5Cl]2+
[Fe(CN)6]4[Fe(H2O)6]2+
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•
•
•
•
[Cu(H2O)6]SO4
[Cr(NH3)5Cl]Cl2
K4[Fe(CN)6]
[Fe(H2O)6](NO3)2
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Ethylene Diamine
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General Chemistry:
Chapter 25
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Copper complex in ligand substitution
add ammonia solution
Cu(H2O)62+
Co(NH3)4(H2O)22+
blue
Add
conc
HCl
deep blue / violet
Add NaOH or NH3 (aq)
CuCl42-
Cu(OH)2
yellow-green
pale blue
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Substitution of ligands
• Ligands can be exchange in the complex
ions.
Cu(H2O)62+ + 2OH-  Cu(OH)2(H2O)4(s) + 2H2O
pale blue
Cu(OH)2(H2O)4(s) + 4NH3  [Cu(H2O)2(NH3)4]2+ +
2H2O + 2OHDeep blue
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Metal Carbonyls
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2002
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General Chemistry:
Chapter 24
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Shape of complex ions
Coordination
number
Shape
Hybridization
Examples
2
4
4
Linear
Tetrahedral
Square
planar
Octahedral
sp
sp3
dsp2
[CuCl2][CuCl4][Ni(CN)4]2-
sp3d2
[Fe(H2O)6]2+
6
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Orbital d
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Oxidation States
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2002
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General Chemistry:
Chapter 24
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Colour of complexes
• Depends on:
– The nature of the central metal ions
– Oxidation state of the central metal ions
– Types of ligands
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Splitting of d orbitals
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• The two d-orbitals [dx2-y2, and dz2] locate
along axes causing a repulsion by the
coming electron from the ligans, as to
compare with the other d-orbitals [dxy,
dyz, dxy] which locate in between axes
having lower repulsion.
• This causes d-orbitals to separate into 2
different energy levels.
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Octahedral Complex and d-Orbital Energies
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2002
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General Chemistry:
Chapter 25
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Electron Configuration in d-Orbitals
Δ
P
Hund’s rule
pairing energy considerations
Δ>P
low spin d4
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Δ<P
high spin d4
General Chemistry:
Chapter 25
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The effect of types of ligand
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Large Δ
Strong field ligands
CN- > NO2- > en > py  NH3 > EDTA4- > SCN- > H2O >
ONO- > ox2- > OH- > F- > SCN- > Cl- > Br- > I-
Small Δ
Weak field ligands
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Transition between d-d* electron
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Geometric Isomerism
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2002
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General Chemistry:
Chapter 25
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conclusion
• A substance appears coloured when
certain wavelength of white light is
absobed. The complementary wavelength
[white light minus the colour absobed]
gives the colour of the substance
• Transition of electron(s) d-d* transition
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Effect of Ligands on the Colors of
Coordination Compounds
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General Chemistry:
Chapter 25
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Homework
• Explain the term homogeneous and
heterogeneous catalyst.
• Give examples and reactions for
homogeneous and heterogeneous
catalyst.
• Compare, qualitatively, the melting point,
density, atomic radius, ionic radius, first
ionization energy and conductivity of the
transition elements with those of calcium
as a typical s-block element.
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Glossary (1/2)
 alloy – A mixture of a metal and at least one other element.
 catalyst – A substance that increases the speed of a
chemical reaction without being used up.
 corrosion – Damage to a metal caused by a chemical or
reaction such as rusting.
 density – A measure of mass in a given volume. Often
expressed in g/dm3.
 ductile – The ability of metals to be drawn into wires.
 lustrous – Bright and shiny.
 malleable – Capable of being bent and pressed into a
different shape.
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Glossary (2/2)
 precipitate – A solid that forms in a solution as a result
of a physical or chemical reaction.
 thermal decomposition – The process by which a
substance is broken down into two or more products by
heating it.
 transition metal – An element located in the block
between groups 2 and 3 of the periodic table.
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Anagrams
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Properties of transition metals
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Multiple-choice quiz
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