10.4.
Chemistry
of Titanium Ti, Z=22,
1s22s22p63s23p63d24s2
data comparison of titanium
with the other members of the 3d–block and transition metals
Z
and symbol |
21
Sc |
22
Ti |
23
V |
24
Cr |
25
Mn |
26
Fe |
27
Co |
28
Ni |
29
Cu |
30
Zn |
property\name |
scandium |
titanium |
vanadium |
chromium |
manganese |
iron |
cobalt |
nickel |
copper |
zinc |
melting
point/oC |
1541 |
1668 |
1910 |
1857 |
1246 |
1538 |
1495 |
1455 |
1083 |
420 |
density/gcm–3 |
2.99 |
4.54 |
6.11 |
7.19 |
7.33 |
7.87 |
8.90 |
8.90 |
8.92 |
7.13 |
atomic
radius/pm |
161 |
145 |
132 |
125 |
124 |
124 |
125 |
125 |
128 |
133 |
M2+
ionic radius/pm |
na |
90 |
88 |
84 |
80 |
76 |
74 |
72 |
69 |
74 |
M3+
ionic radius/pm |
81 |
76 |
74 |
69 |
66 |
64 |
63 |
62 |
na |
na |
common oxidation
states |
+3
only |
+2,3,4 |
+2,3,4,5 |
+2,3,6 |
+2,3,4,6,7 |
+2,3,6 |
+2,3 |
+2,+3 |
+1,2 |
+2
only |
outer electron config.[Ar]... |
3d14s2 |
3d24s2 |
3d34s2 |
3d54s1 |
3d54s2 |
3d64s2 |
3d74s2 |
3d84s2 |
3d104s1 |
3d104s2 |
Elect.
pot. M(s)/M2+(aq) |
na |
–1.63V |
–1.18V |
–0.90V |
–1.18V |
–0.44V |
–0.28V |
–0.26V |
+0.34V |
–0.76V |
Elect.
pot. M(s)/M3+(aq) |
–2.03V |
–1.21V |
–0.85V |
–0.74V |
–0.28V |
–0.04V |
+0.40 |
na |
na |
na |
Elect.
pot. M2+(aq)/M3+(aq) |
na |
–0.37V |
–0.26V |
–0.42V |
+1.52V |
+0.77V |
+1.87V |
na |
na |
na |
Elect.
pot. = standard electrode potential data for titanium
(EØ at 298K/25oC, 101kPa/1 atm.)
na = data not applicable to titanium
Extended data table for TITANIUM
property of titanium/unit |
value for Ti |
Ti melting
point/oC |
1668 |
Ti boiling
point/oC |
3287 |
density of Ti/gcm–3 |
4.54 |
1st
Ionisation Energy/kJmol–1 |
658 |
2nd
IE/kJmol–1 |
1310 |
3rd
IE/kJmol–1 |
2652 |
4th
IE/kJmol–1 |
4175 |
5th
IE/kJmol–1 |
9573 |
atomic
radius Ti/pm |
145 |
Ti2+
ionic radius/pm |
90 |
Relative polarising power Ti2+ ion |
2.2 |
Ti3+
ionic radius/pm |
76 |
Relative polarising power Ti3+ ion |
3.9 |
Ti4+
ionic radius/pm |
68 |
Polarising power Ti4+ ion |
5.9 |
oxidation
states of Ti,
less common/stable |
+2, +3, +4 |
simple electron
configuration of Ti |
2,8,10,2 |
outer electrons of Ti [beyond
argon core] |
[Ar]3d24s2 |
Electrode
potential Ti(s)/Ti2+(aq) |
–1.63V |
Electrode
potential Ti(s)/Ti3+(aq) |
–1.21V |
Electrode
potential Ti2+(aq)/M3+(aq) |
–0.37V |
Electronegativity of Ti |
1.54 |
-
Extraction of titanium
-
Titanium ore is mainly
the oxide TiO2, which is
converted into the covalent liquid
titanium tetrachloride TiCl4 by heating
with carbon and chlorine. There is no change in oxidation state of
titanium in this reaction (+4 in both compounds involved). Titanium(IV)
chloride has a tetrahedral shape.
-
The chloride is then reacted
with sodium or magnesium to form titanium metal and sodium chloride
or magnesium Chloride.
-
This reaction is carried
out in an atmosphere of inert argon gas so non of the metals
involved becomes oxidised by atmospheric oxygen.
-
TiCl4 +
2Mg ==> Ti + 2MgCl2 or
TiCl4
+ 4Na ==> Ti + 4NaCl
-
Overall the titanium
oxide ore is reduced to titanium metal (overall O loss, oxide
=> metal) and the magnesium or sodium acts as a reducing agent.
-
Uses of TITANIUM
-
Titanium is a hard
silvery–white lustrous metal of relatively low density.
-
Titanium is relatively
resistant to corrosion and is a very
important metal for various specialised uses.
-
Titanium carbide, TiC, is
used in making extremely hard alloys for high speed tools e.g. the drill
bit.
-
Titanium alloys are
amongst the strongest and lightest of metal alloys.
-
It is used in
aeroplanes, in nuclear reactor alloys, chemical reactor vessels and for replacement hip
joints.
-
With a lighter
density of 4.4 g/cm3 compared to steel (~7.9 g/cm3) its
just as strong as steel and with the added advantage of being
unreactive towards oxygen and water at room temperature so does
not suffer the rusting of iron corrosion.
-
Titanium(IV)
oxide, TiO2, is an important white pigment used in the paints
industry.
-
Titanium(IV) oxide is also
used in paper making, ceramics and textile industries.
-
Titanium(IV) chloride and
other covalent titanium compounds are used as polymerisation catalysts
(e.g. Ziegler–Natta catalysts) for manufacturing polyalkenes like
poly(propene).
The Chemistry
of TITANIUM
Pd |
s block |
d blocks (3d
block
scandium)
and
f
blocks of
metallic elements |
p block elements |
Gp1 |
Gp2 |
Gp3/13 |
Gp4/14 |
1 |
1H
|
2 |
3Li |
4Be |
Part of the modern Periodic Table of Elements:
ZSymbol, z = atomic or proton
number
Sc to Zn are now
considered the head-top elements of groups 3 to 12
3d
block of metallic elements: Scandium to Zinc
focus on scandium |
5B |
6C |
3 |
11Na |
12Mg |
13Al |
14Si |
4 |
19K |
20Ca |
21Sc
[Ar]3d14s2
scandium |
22Ti
[Ar]3d24s2
titanium |
23V
[Ar] 3d34s2
vanadium |
24Cr
[Ar] 3d54s1
chromium |
25Mn
[Ar] 3d54s2
manganese |
26Fe
[Ar] 3d64s2
iron |
27Co
[Ar] 3d74s2
cobalt |
28Ni
[Ar] 3d84s2
nickel |
29Cu
[Ar] 3d104s1
copper |
30Zn
[Ar] 3d104s2
zinc |
31Ga |
32Ge |
5 |
37Rb |
38Sr |
39Y |
40Zr |
41Nb |
42Mo |
43Tc |
44Ru |
45Rh |
46Pd |
47Ag |
48Cd |
49In |
50Sn |
6 |
55Cs |
56Ba |
57,58-71 |
72Hf |
73Ta |
74W |
75Re |
76Os |
77Ir |
78Pt |
79Au |
80Hg |
81Tl |
82Pb |
7 |
87Fr |
88Ra |
89,90-103 |
104Rf |
105Db |
106Sg |
107Bh |
108Hs |
109Mt |
110Ds |
111Rg |
112Cn |
113Nh |
114Fl |
Summary of
oxidation
states of the 3d block metals (least important) Ti to Cu are true
transition metals |
Sc |
Ti |
V |
Cr |
Mn |
Fe |
Co |
Ni |
Cu |
Zn |
|
|
|
|
|
|
|
|
+1 |
|
|
(+2) (3d2) |
(+2) |
(+2) |
+2 |
+2 |
+2 |
+2 |
+2 |
+2 |
+3 |
+3 (3d1) |
+3 |
+3 |
(+3) |
+3 |
+3 |
(+3) |
(+3) |
|
|
+4 (3d0) |
+4 |
|
+4 |
|
|
(+4) |
|
|
|
|
+5 |
|
|
|
|
|
|
|
|
|
|
+6 |
(+6) |
(+6) |
|
|
|
|
|
|
|
|
+7 |
|
|
|
|
|
3d14s2 |
3d24s2 |
3d34s2 |
3d54s1 |
3d54s2 |
3d64s2 |
3d74s2 |
3d84s2 |
3d104s1 |
3d104s2 |
The outer electron configurations beyond [Ar]
and the
(ground state of the simple
ion)
Note that when 3d block
elements form ions,
the 4s electrons are 'lost' first. |
The oxidation states and electron
configuration of
titanium
in the context of the 3d block of elements
The
electrode potential chart highlights the values for various
oxidation states of titanium.
The electrode potentials involving titanium
ions correspond to hydrated complex ions where the ligands
are water, oxide or hydroxide.
As you can see from the chart, changing
either the ligand or the oxidation state, will also change
the electrode potential for that half-reaction involving a
titanium ion.
Titanium(II) compounds are readily oxidised to titanium(III) and titanium(IV) compounds.
The hexaaquatitanium(II) ion is a strong
reducing agent.
Titanium extraction
and Ti(IV) CHEMISTRY
-
It is more
difficult to extract from its ore than other more common metals so
is not cheap!
-
Titanium is extracted from the raw material
rutile ore which contains titanium dioxide.
-
Carbon reduction of
the oxide to the metal is not that practical due to titanium carbide
formation so the titanium(IV) oxide is initially converted to
titanium(IV) chloride which is then reduced to the metal with a more
reactive metal in a displacement reaction.
-
The rutile
titanium oxide ore is heated with carbon and chlorine to
make titanium(IV) chloride
-
After the oxide is
converted into TiCl4 which is then reacted with sodium or
magnesium to form titanium metal and sodium chloride or magnesium
Chloride. The sodium and magnesium act as the reducing agent
in this batch process.
-
This reaction is
carried
out in an atmosphere of inert argon gas so non of the
metals involved becomes oxidised by atmospheric oxygen.
-
These are
examples of metal displacement reactions e.g. the less
reactive titanium is displaced by the more reactive sodium or
magnesium.
-
Overall the titanium
oxide ore is reduced to titanium metal (overall O loss
from ox. state +4, oxide => metal with ox. state 0)
-
TiCl4
is covalent liquid which (i) hydrolyses back to the oxide in
water.
-
Note that Ti4+
has a [Ar]3d0 structure, hence, with no 3d electrons it
is colourless.
-
-
Diagram showing why Ti4+ is colourless and Ti3+
is coloured.
-
In the ground state of the
titanium(IV) ion,
[Ar]3d0, despite the possible 3d orbital splitting,
there is no 3d electron
to be promoted, so no absorption of visible light photons and
all visible light transmitted, so no colour!
-
However, in the case of the titanium(III) ion,
[Ar]3d1,
there is a 3d electron capable of being promoted to a higher
quantum state, from the energy of a visible light photon,
resulting in absorption and transmission giving a violet colour.
-
(See
colour theory of transition metal
compound) for explaining why most titanium compounds
with an oxidation state of +4 are usually colourless.
-
See
uv-visible absorption
spectra of selected titanium complex ions & compounds
for detailed discussion
-
Hydrated TiO2 dissolves in conc.
hydrofluoric acid to give a colourless solution of the hexafluorotitanate(IV)
ion, an octahedral shaped complex with the formula
[TiF6]2-(aq)
-
The hexachlorotitanate(IV) ion, another octahedral
shaped complex with the formula [TiCl6]2-(aq)
also exists, but is pale yellow.
-
When titanium(IV)
compounds are dissolved in water or acid the oxo–cation [TiO]2+(aq)
is formed.
-
The
electrode potential chart highlights the values for various
oxidation states of titanium.
TITANIUM(III) CHEMISTRY
-
Electron configuration of the
titanium(III) ion Ti3+
is [Ar]3d1
-
Titanium(III) compounds can be
obtained from Ti(IV) salts by using a zinc/dil. sulfuric acid
reducing agent.
-
eg the colourless
oxotitanium(IV) ion is reduced to the purple
hexaaquatitanium(III) ion
-
colourless
Ti(IV) as [TiO]2+
==> Ti(III) in acid solution giving the
purple [Ti(H2O)6)]3+(aq)
-
but it is readily
oxidised back to Ti(IV) by dissolved oxygen from the atmosphere
-
Titanium(III) chloride TiCl3 is a
violet solid.
-
-
Diagram showing why Ti3+ is coloured and Ti4+
is colourless.
-
In the case of the aqueous hexaaquatitanium(III) ion,
[Ar]3d1,
there a 3d electron can be promoted to a higher
quantum state, from the energy of a visible light photon,
resulting in absorption and transmission giving a violet colour.
-
See also the
uv-visible absorption
spectra of selected titanium complex ions and compounds
TITANIUM(II) CHEMISTRY
-
Electron configuration of the
titanium(II) ion Ti2+
is [Ar]3d2
-
Titanium(II) chloride TiCl2 is a black
solid.
-
The
octahedral
violet hexaaquatitanium(II) ion [Ti(H2O)6)]2+
ion can be formed by reducing Ti(IV) or Ti(III) with a metal/acid
mixture but it is very unstable in redox terms, ie readily oxidised by
dissolved oxygen from the atmosphere.
-
Ti2+, a powerful
reducing agent, will reduce
water to hydrogen (i.e. oxidised by water to Ti3+) and
because it is rapidly oxidised by air
it is not very stable in aqueous solution.
-
From the electrode
potential chart you can see that the electrode potential of Ti3+/Ti2+
is –0.37V and is far less
positive than electrode potential of O2/H+/H2O +1.23V in acid
solution.
-
See also the
uv-visible absorption
spectra of selected titanium complex ions and compounds
Appendix: More on how
titanium is produced and what is it used for?
Titanium is a very important
metal for various specialised uses. It is more difficult to extract
from its ore than other, more common metals.
-
Titanium is a transition metal
of low density ('light'), strong and resistant to corrosion.
-
Titanium alloys are
amongst the strongest lightest of metal alloys and used in aircraft
production.
-
There is a note
about
the bonding and structure
of alloys on another page.
-
As well as its use in aeroplanes
it is an important component in
nuclear reactor alloys and for replacement hip joints because of its
light and strong nature AND it doesn't easily corrode.
-
It is one of
the main components of Nitinol 'smart' alloys. Nitinol
belongs to a group of shape memory alloys (SMA) which can
'remember their original shape'. For example they can regain
there original shape on heating (e.g. used in thermostats in
cookers , coffer makers etc.) or after release of a physical
stress (e.g. used in 'bendable' eyeglass frames, very handy if
you tread on them!). The other main metal used in these very
useful intermetallic compounds is nickel.
-
Titanium is extracted
from the raw material
is the ore rutile which contains titanium dioxide.
-
The rutile
titanium oxide ore is
heated with carbon and chlorine to make titanium(IV) chloride (titanium
tetrachloride)
-
After the oxide is
converted into titanium chloride TiCl4, it is then reacted with sodium or
magnesium to form titanium metal and sodium chloride or magnesium
Chloride. This is an expensive process because sodium or
magnesium are manufactured by the costly process of electrolysis
(electricity is the most costly form of energy).
-
This reaction is carried out in an atmosphere of inert argon
gas so none of the metals involved becomes oxidised by atmospheric
oxygen.
-
TiCl4 +
2Mg ==> Ti + 2MgCl2 or
TiCl4
+ 4Na ==> Ti + 4NaCl
-
These are examples of
metal displacement reactions e.g. the less reactive titanium is displaced by the more reactive sodium or magnesium.
-
Overall the
titanium oxide ore is reduced to titanium metal (overall O
loss, oxide => metal)
-
Metals can become weakened
when repeatedly stressed and strained. This can lead to faults
developing in the metal structure called 'metal fatigue' or
'stress fractures'.
-
If the metal fatigue is significant it can lead to
the collapse of a metal structure.
-
So it is important develop alloys
which are well designed, well tested and will last the expected lifetime
of the structure whether it be part of an aircraft (eg titanium aircraft
frame) or a part of a bridge (eg steel suspension cables).
-
There are many applications of
titanium alloys
in the industrial, automotive and aerospace fields and
titanium has been widely used for implant devices that replace patients’
hard tissues eg in orthopaedic surgery techniques. It is accepted that
commercially pure Ti is a highly biocompatible material due to the
spontaneous build-up of an inert and stable oxide layer [Titanium(IV)
oxide, TiO2].
-
Additional properties that make Ti
suitable for biomedical applications include high strength-to-weight
ratio, relatively low electrical conductivity, low ion-formation levels
in aqueous environments (eg soft tissue).
-
Titanium is one of a few materials
capable of osseointegration, which means it exhibits mechanical
retention of the implant by the host bone tissue, which stabilizes the
implant without any soft tissue layers between the two.
-
These properties enable a wide use of
titanium for devices such as artificial knee and hip joints, screws and
shunts for fracture fixation, bone plates, pacemakers and cardiac valve
prosthesis and dental applications of Ti are just as common, including
implants and their components such as inlays, crowns, overdentures, and
bridges.
-
However, the pure titanium is not
strong enough for a number of medical purposes and there is a need for
developing more superior Ti-based alloys.
-
Apparently Ti exhibits poor
machineability, which reduces tool life, increases the processing time
and is problematic when the elimination of a dental Ti prosthesis is
necessary. Both the machineability and hardness can be improved by
alloying Ti with another element eg gold.
-
A number of toxic effects were
reported in permanent implants [using vanadium and aluminium containing
titanium alloys was discontinued.
-
Among biocompatible elements, the
addition of Ag and Cu nearly doubles the hardness, compared to pure
titanium.
-
Titanium-gold alloys are
extremely tough and hard and have biomedical applications.
-
There is a constant search for
materials for use in orthopaedic medicine and those materials, including
titanium alloys, which have a high degree of biocompatibility - that is
those that give none or minimal adverse effects on interacting with
human tissue.
-
The high biocompatibility and
corrosion resistance of Au may yield an alloy suitable for
biomedical purposes. In case the machineability decreases with
increased hardness, the relatively low melting temperatures of Ti-Au
alloys will allow for the majority of parts to be produced by
casting in moulds.
-
Ti-Au alloys can adhere to a
ceramic surface, making it convenient for a number of biomedical
applications, reducing the overall weight and cost of the
corresponding parts.
-
Titanium-gold alloys exhibit extreme
hardness and strength values, reduced density compared to gold, high
malleability, high biocompatibility, low wear, reduced
friction, potentially high radio opacity, as well as osseointegration.
-
All these properties render the Ti-Au
alloys particularly useful for orthopaedic, dental, and prosthetic
applications, where they could be used as both permanent and temporary
components.
|
keywords redox reactions ligand
substitution reactions of titanium ions displacement balanced equations
formula complex ions complexes ligand exchange reactions redox reactions ligands
colours reactions and oxidation states of titanium ions Ti2+ Ti3+ Ti4+ Ti(+2) Ti(II) Ti(+3)
Ti(III) Ti(+4) Ti(IV) TiCl4 + 2Mg ==> Ti + 2MgCl2 or TiCl4 + 4Na ==> Ti + 4NaCl
TiO2 + 2Cl2 + C ==> TiCl4 + CO2 TiCl4 + 2Mg ==> Ti + 2MgCl2 or TiCl4 + 4Na ==>
Ti + 4NaCl TiCl4 + 2H2O(l) ==> TiO2 + 4HCl TiCl4 + 2Cl–(aq) ==> [TiCl6)]2–
[Ti(H2O)6)]3+ [Ti(H2O)6)]2+ Ti3+/Ti2+ oxidation states of titanium, redox
reactions of titanium, ligand substitution displacement reactions of titanium,
balanced equations of titanium chemistry, formula of titanium complex ions,
shapes colours of titanium complexes chemistry of titanium notes
for AQA AS chemistry, chemistry of titanium notes
for Edexcel A level AS chemistry, chemistry of titanium notes for A level OCR AS chemistry A,
chemistry of titanium notes for OCR Salters AS chemistry B,
chemistry of titanium notes for AQA A level chemistry,
chemistry of titanium notes for A level Edexcel A level chemistry,
chemistry of titanium notes for OCR A level chemistry
A, chemistry of titanium notes for A level OCR Salters A
level chemistry B chemistry of titanium notes for US Honours grade 11 grade 12
chemistry of titanium notes for
pre-university chemistry courses pre-university A level revision
notes for chemistry of titanium notes A level guide
notes on chemistry of titanium notes for schools colleges academies science course tutors images
pictures diagrams for chemistry of titanium notes A level chemistry revision notes on
chemistry of titanium notes for revising module topics notes to help on understanding of
chemistry of titanium notes university courses in science
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apprenticeships technical internships USA US grade 11 grade 11 AQA A
level chemistry
notes on chemistry of titanium notes Edexcel
A level chemistry notes on chemistry of titanium notes for OCR A level chemistry
notes WJEC A level chemistry notes on chemistry of titanium
notes CCEA/CEA A level
chemistry notes on chemistry of titanium notes for university entrance examinations
balanced equations for the reactions of titanium details of the extraction of
titanium, explaining why titanium(IV) compounds are white solids or colourless
liquids or titanium(IV) complexes are colourless in aqueous solution
WHAT NEXT?
GCSE Level Notes on Transition
Metals (for the basics)
The chemistry of
Scandium
* Titanium * Vanadium
* Chromium
* Manganese
The chemistry of
Iron * Cobalt
* Nickel
* Copper *
Zinc
*
Silver & Platinum
Introduction 3d–block Transition Metals * Appendix
1.
Hydrated salts, acidity of
hexa–aqua ions * Appendix 2. Complexes
& ligands * Appendix 3. Complexes and isomerism * Appendix 4.
Electron configuration & colour theory * Appendix 5. Redox
equations, feasibility, Eø * Appendix 6.
Catalysis * Appendix 7.
Redox
equations
* Appendix 8. Stability Constants and entropy
changes *
Appendix 9. Colorimetric analysis
and complex ion formula * Appendix 10 3d block
– extended data
* Appendix 11 Some 3d–block compounds, complexes, oxidation states
& electrode potentials * Appendix 12
Hydroxide complex precipitate 'pictures',
formulae and equations
Some
pages have a matching sub-index
Advanced
Level Inorganic Chemistry Periodic Table Index:
Part 1
Periodic Table history
Part 2
Electron configurations, spectroscopy,
hydrogen spectrum,
ionisation energies *
Part 3
Period 1 survey H to He *
Part 4
Period 2 survey Li to Ne * Part
5 Period 3 survey Na to Ar *
Part 6
Period 4 survey K to Kr AND important
trends down a group *
Part 7
s–block Groups 1/2 Alkali Metals/Alkaline Earth Metals *
Part 8
p–block Groups 3/13 to 0/18 *
Part 9
Group 7/17 The Halogens *
Part 10
3d block elements & Transition Metal Series
*
Part 11
Group & Series data & periodicity plots
All
11 Parts have
their own sub-indexes near the top of the pages
Group numbering and the modern periodic
table
The original group numbers of
the periodic table ran from group 1 alkali metals to group 0
noble gases. To account for the d block elements and their
'vertical' similarities, in the modern periodic table, groups 3
to group 0 are numbered 13 to 18. So, the p block elements are
referred to as groups 13 to group 18 at a higher academic level,
though the group 3 to 0 notation is still
used, but usually at a lower academic level. The 3d block
elements (Sc to Zn) are now considered the head (top) elements
of groups 3 to 12.
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worksheets etc. Copying of website material is NOT permitted. Doc
Brown's Chemistry theoretical-physical chemistry revision notes for
pre-university level students on d-block elements including the
physical and chemical properties reactions equations and trends
explained for the 3d-block of transition metals series
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