Transcript COLOURED IONS a solution of copper(II)sulphate is blue because

AN INTRODUCTION TO
TRANSITION METAL
CHEMISTRY
KNOCKHARDY PUBLISHING
KNOCKHARDY PUBLISHING
TRANSITION METALS
INTRODUCTION
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TRANSITION METALS
CONTENTS
• Definition
• Metallic properties
• Electronic configurations
• Variable oxidation state
• Coloured ions
• Complex ion formation
• Shapes of complexes
• Isomerism in complexes
• Catalytic properties
• Revision check list
TRANSITION METALS
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
THE FIRST ROW TRANSITION ELEMENTS
Definition
D-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
THE FIRST ROW TRANSITION ELEMENTS
Definition
D-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
properties
all 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
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
POTASSIUM
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
3d
4s
3
3p
1s2 2s2 2p6 3s2 3p6 4s1
‘Aufbau’
Principle
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.
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
CALCIUM
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
3d
4s
3
3p
1s2 2s2 2p6 3s2 3p6 4s2
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 -s1 electronic configuration are
in Group I and all with an -s2 configuration are in Group II.
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
SCANDIUM
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
3d
4s
3
3p
1s2 2s2 2p6 3s2 3p6 4s2 3d1
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.
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
TITANIUM
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
3d
4s
3
3p
1s2 2s2 2p6 3s2 3p6 4s2 3d2
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
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
VANADIUM
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
3d
4s
3
3p
1s2 2s2 2p6 3s2 3p6 4s2 3d3
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
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
CHROMIUM
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
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.
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
MANGANESE
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
3d
4s
3
3p
1s2 2s2 2p6 3s2 3p6 4s2 3d5
The new electron goes into the 4s to restore its filled state.
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
IRON
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
3d
4s
3
3p
1s2 2s2 2p6 3s2 3p6 4s2 3d6
Orbitals are filled according to Hund’s Rule. They continue to pair up.
HUND’S RULE OF
MAXIMUM MULTIPLICITY
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
COBALT
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
3d
4s
3
3p
1s2 2s2 2p6 3s2 3p6 4s2 3d7
Orbitals are filled according to Hund’s Rule. They continue to pair up.
HUND’S RULE OF
MAXIMUM MULTIPLICITY
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
NICKEL
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
3d
4s
3
3p
1s2 2s2 2p6 3s2 3p6 4s2 3d8
Orbitals are filled according to Hund’s Rule. They continue to pair up.
HUND’S RULE OF
MAXIMUM MULTIPLICITY
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
COPPER
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
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.
HUND’S RULE OF
MAXIMUM MULTIPLICITY
ELECTRONIC CONFIGURATIONS OF THE FIRST ROW TRANSITION METALS
ZINC
INCREASING ENERGY /
DISTANCE FROM
NUCLEUS
4f
4
4d
4p
3d
4s
3
3p
1s2 2s2 2p6 3s2 3p6 4s2 3d10
The electron goes into the 4s to restore its filled state and complete the 3d and 4s
orbital filling.
ELECTRONIC CONFIGURATIONS
K
1s2 2s2 2p6 3s2 3p6 4s1
Ca
1s2 2s2 2p6 3s2 3p6 4s2
Sc
1s2 2s2 2p6 3s2 3p6 4s2 3d1
Ti
1s2 2s2 2p6 3s2 3p6 4s2 3d2
V
1s2 2s2 2p6 3s2 3p6 4s2 3d3
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
VARIABLE OXIDATION STATES
Arises from the similar energies required for removal of 4s and 3d electrons
maximum rises across row to manganese
Sc
Ti
V
Cr Mn Fe Co Ni
+7
maximum falls as the energy required to
remove more electrons becomes very high
+6 +6 +6
+5 +5 +5 +5
all (except scandium) have an
M2+
ion
stability of +2 state increases across the row
due to increase in the 3rd Ionisation Energy
Cu Zn
+4 +4 +4
+3 +3
+2
+3 +3
+2
+4 +4
+5
+4 +4
+3 +3 +3
+2 +2 +2 +2
+3
+2 +2 +2
+1
THE MOST IMPORTANT STATES ARE IN RED
When electrons are removed they come from the 4s orbitals first
Cu
Cu+
Cu2+
1s2 2s2 2p6 3s2 3p6 3d10 4s1
1s2 2s2 2p6 3s2 3p6 3d10
1s2 2s2 2p6 3s2 3p6 3d9
Ti
Ti2+
Ti3+
Ti4+
1s2 2s2 2p6 3s2 3p6 3d2 4s2
1s2 2s2 2p6 3s2 3p6 3d2
1s2 2s 2p6 3s2 3p6 3d1
1s2 2s2 2p6 3s2 3p6
COLOURED IONS
A characteristic of transition metals is their ability to form coloured compounds
Theory
ions with a d10 (full) or d0 (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
or
d10 (full) Cu+,Ag+ Zn2+
d0 (empty) Sc3+ configuration are colourless
e.g. titanium(IV) oxide TiO2 is white
colour depends on ...
transition element
oxidation state
ligand
coordination number
3d ORBITALS
There are 5 different orbitals of the d variety
xy
xz
x2-y2
yz
z2
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 (z2 and x2-y2) go higher and three go lower
In a tetrahedral complex, three (xy, xz and yz) go higher and two go lower
OCTAHEDRAL
TETRAHEDRAL
3d
3d
Degree of splitting depends on the
CENTRAL 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.
COLOURED IONS
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
Absorbed colour
VIOLET
BLUE
BLUE-GREEN
YELLOW-GREEN
YELLOW
ORANGE
RED
nm
400
450
490
570
580
600
650
Observed colour
GREEN-YELLOW
YELLOW
RED
VIOLET
DARK BLUE
BLUE
GREEN
nm
560
600
620
410
430
450
520
COLOURED IONS
a solution of copper(II)sulphate is blue because
red and yellow wavelengths are absorbed
white light
blue and green
not absorbed
COLOURED IONS
a solution of copper(II)sulphate is blue because
red and yellow wavelengths are absorbed
COLOURED IONS
a solution of copper(II)sulphate is blue because
red and yellow wavelengths are absorbed
COLOURED IONS
a solution of nickel(II)sulphate is green because
violet, blue and red wavelengths are absorbed
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
RED
LIGHT
WHITE
LIGHT
BLUE
FILTER
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
Light 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 Fe3+
and SCN¯ is 1:1.
This shows the complex has
the formula [Fe(H2O)5SCN]2+
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 Ni2+
and edta is 1:1.
COMPLEX IONS - LIGANDS
Formation
ligands form co-ordinate bonds to a central transition metal ion
Ligands
atoms, 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
chloride
cyanide
hydroxide
oxide
water
ammonia
Formula
Cl¯
NC¯
HO¯
O2H2O
NH3
Name of ligand
chloro
cyano
hydroxo
oxo
aqua
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
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
Unidentate
form one co-ordinate bond
Cl¯, OH¯, CN¯, NH3, and H2O
Bidentate
form two co-ordinate bonds
H2NCH2CH2NH2 , C2O42-
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
Multidentate
form several co-ordinate bonds
EDTA
An important complexing agent
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
Multidentate
form 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
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
Multidentate
form several co-ordinate bonds
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.
Shape
Example(s)
6
Octahedral
[Cu(H2O)6]2+
4
Tetrahedral
[CuCl4]2-
2
Square planar
Pt(NH3)2Cl2
Linear
[Ag(NH3)2]+
ISOMERISATION IN COMPLEXES
Some octahedral complexes can exist in more than one form
[MA4B2]n+
TRANS
[MA3B3]n+
CIS
ISOMERISATION IN COMPLEXES
GEOMETRICAL ISOMERISM
Square planar complexes of the form [MA2B2]n+ exist in two forms
trans platin
cis platin
An important anti-cancer drug. It
is a square planar, 4 co-ordinate
complex of platinum.
ISOMERISATION IN COMPLEXES
OPTICAL ISOMERISM
Some octahedral complexes exist in two forms
Octahedral complexes with bidentate ligands can
exist as a pair of enantiomers (optical isomers)
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
IRON
Manufacture of ammonia - Haber Process
NICKEL
Hydrogenation reactions - margarine manufacture
RHODIUM
Catalytic converters
VANADIUM(V) OXIDE
Manufacture of sulphuric acid - Contact Process
REVISION CHECK
What should you be able to do?
Recall and explain the typical properties of transition metals and their ions
Recall and explain the electronic configurations of the first row transition elements
Recall and explain the origin of colour in compounds and complex ions
Recall and explain the shape of complex ions
Recall and explain the possibilities for isomerism in complexes
Recall examples of catalysis involving transition metals and their compounds
CAN YOU DO ALL OF THESE?
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AN INTRODUCTION TO
TRANSITION METAL
CHEMISTRY
THE END
© JONATHAN HOPTON & KNOCKHARDY PUBLISHING