|
  Doc
Brown's Chemistry Clinic
Transition Metal Elements
KS4 Science-CHEMISTRY GCSE-IGCSE
revision information
notes data
Detailed
GCE-AS-A2-IB Advanced Level Notes 3d block Transition Metals
PAGE index LINKS:
(a)-(c)
Physical properties * (d)
Chemical-reactions properties *
(e) Use
as catalysts * (f) More on uses of Transition Metals/compounds/alloys * (g)
Note on uses of other non-transition metals/alloys e.g. aluminium/duralumin
(Al is NOT
a transition metal)
LINKS to other related
pages relating to metals: Extra
GCSE
Industrial Chemistry * GCSE Notes on Metal Extraction *
GCSE Notes on Metal
Reactivity * GCSE Notes on Periodic Table *
GCSE Notes on steel
making, alloy uses and other metal uses * Transition
Metal m/c QUIZ *
multi-word fill quiz
* GCSE notes on Group 1 Alkali Metals
* Detailed Advanced Level Notes on the
3d-block Transition Metals * Detailed AS-A2 Advanced Level Notes on s-block Gps 1-2 Metals *
EMAIL query?comment
Some Reminders about the
Periodic Table
- The elements are laid out in order of
Atomic Number
- Hydrogen, 1, H,
does not readily fit into any group
- A Group is a vertical column of like elements
e.g. Group 1 The Alkali Metals (Li, Na, K etc.), Group 7 The Halogens (F, Cl, Br, I etc.) and Group 8 or 0 The Noble Gases (He, Ne, Ar etc.). The group number equals the number of electrons in the outer
shell (e.g. chlorine's electron arrangement is 2.8.7, the second element down in Group 7).
- A Period is a complete horizontal row of elements with a variety of properties (more metallic to more
non-metallic from left to right). All the elements use the same number of electron shells which equals the period number (e.g. sodium's electron arrangement 2.8.1, the first element in Period 3).
- On Period 4 is a horizontal row of ten elements between Group 2 and Group 3,
and from Sc to Zn are called the first
Transition Metals Series of Elements
-
A
summary of some TRANSITION METAL DATA
e.g. melting/boiling points,
densities and more advanced data, is on another webpage and is suitable
for GCSE, AS, A2 and US grades 9-12 courses.
The Typical Characteristics of 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
pt./oC |
1541 |
1668 |
1910 |
1857 |
1246 |
1538 |
1495 |
1455 |
1083 |
420 |
|
boiling
pt./oC |
2836 |
3287 |
3380 |
2672 |
1962 |
2861 |
2870 |
2730 |
2567 |
907 |
|
density/gcm-3 |
2.99 |
4.54 |
6.11 |
7.19 |
7.33 |
7.87 |
8.90 |
8.90 |
8.92 |
7.13 |
(a) Some General
Physical Characteristics
-
Generally speaking they are
hard, tough and strong (compared with the Group 1 Alkali metals!)
because of the strong metallic atom-atom bonding.
-
Good conductors of heat and
electricity
(there have many free electrons per atom to carry thermal or electrical
energy ).They are easily
hammered and bent into shape.
They are typically
lustrous/shiny solids (or liquids).
(b) High Melting Point and Boiling Point
- The bonding between the atoms in transition metals is very
strong (bonding notes). The strong attractive force between the atoms is only weakened at high temperatures, hence the high melting points and boiling
points (again compare with Group 1 Alkali Metals).
- Mercury is in another
transition metal, but unusually, it has a very low melting point of -39oC.
For example: iron melts at 1535°C and boils at 2750°C BUT a Group 1 Alkali
Metal such as sodium melts at 98°C and boils at 883°C.
(c) High density
- Another consequence of the strong bonding between the atoms in transition metals is
that they are tightly held together to give a high density.
- For example: iron has a density of 7.9 g/cm3 and sodium has a density of 0.97 g/cm3(and floats on water while fizzing! water has a density of 1.0 g/cm3).
(d)(i) Form coloured compounds and ions in solution
They tend to be much less reactive than the Alkali Metals. They do not react as quickly with water or oxygen so do
not corrode as quickly. Transition metals tend to form more coloured compounds more than other elements either in solid form or dissolved in a solvent
like water. Examples of the colours
of some transition metal salts in aqueous solution are shown below. These
coloured ions/compounds often have quite a complex structure and indeed called
complexes.
1 2 3 4 5 6 7 8 9 10
- Sc - scandium salts, such as the chloride, ScCl3, are colourless and
are not typical of transition metals
- Ti - titanium(III) chloride, TiCl3, is purple
- V - vanadium(III) chloride, VCl3, is green
- Cr - chromium(III) sulphate, Cr2(SO4)3, is dark green
(chromate(VI) salts are yellow, dichromate(VI) salts are orange)
- Mn - manganese compound - potassium manganate(VII), KMnO4, is purple
(manganese(II) salts eg MnCl2 are pale pink)
- Fe - iron(III) chloride, FeCl3, is yellow-orange-brown.
- Iron(II) compounds are usually light green and
iron(III) compounds orange/brown.
- Co - cobalt sulphate, CoSO4, is pinkish
- Ni - nickel chloride, NiCl2, is green
- Cu - copper(II) sulphate, CuSO4, is blue.
- Most common copper compounds are
blue
in their crystals or solution
and sometimes green.
- The blue
aqueous copper ion, Cu2+(aq), actually
has a more complicated structure:
- *[Cu(H2O)6]2+(aq) and when excess
ammonia solution is added,
- after the
initial gelatinous blue copper(II) hydroxide precipitate is formed,
Cu(OH)2,
- it dissolves
to form the deep royal blue ion:
*[Cu(H2O)2(NH3)4]2+(aq).
-
*are called complex
ions and when coloured are typical of transition metal
chemistry.
- Copper(II)
oxide, CuO, black insoluble solid, readily dissolving in acids to give
soluble
blue salts e.g.
- copper(II)
sulphate, CuSO4, from dilute sulphuric acid,
- copper(II)
nitrate, Cu(NO3)2, from dilute nitric acid
- and greeny-blue
copper(II) chloride, CuCl2, from dilute hydrochloric
acid.
- Copper(II)
hydroxide, Cu(OH)2, blue gelatinous precipitate formed when
alkali added to copper salt solutions.
- Copper(II) carbonate, CuCO3,
is turquoise-green insoluble solid, readily dissolving in acids,
evolving carbon dioxide, to give soluble
blue salts (see above)
Copper's valency or combining
power is usually two e.g. compounds containing the Cu2+
ion. However there are copper(I) compounds where the valency is one.
This variable valency, hence compounds of the same elements, but
with different formulae, is typical of transition metal compounds
e.g.
- copper(I) oxide, Cu2O,
an insoluble red-brown solid,
- or copper(I) sulphate, Cu2SO4,
a white solid.
- Zn - zinc salts such as zinc sulphate, ZnSO4, are usually colourless and
are not typical of transition metals.
(d)(ii) Some
other odd bits of chemistry
(for some
gcse/igcse chemistry courses)
-
See
Acids,
Bases and Salts page for the preparation of Transition
Metal Salts
from
insoluble oxides, hydroxides or carbonates (insoluble bases).
-
Many of the transition metal
carbonates are unstable on heating
and readily undergo thermal
decomposition.
-
metal carbonate ==>
metal oxide + carbon dioxide -
e.g. copper(II)
carbonate ==>
copper(II) oxide + carbon dioxide -
or
zinc carbonate ==> zinc
oxide + carbon dioxide-
MCO3(s) ==>
MO(s) + CO2(g) where M could be Fe, Cu, Mn or Zn
-
The carbon dioxide can be
confirmed by giving a white milky precipitate with limewater.
-
Sometimes the two solids
show a colour change eg
-
for M = Cu: turquoise
green carbonate ==> black
copper(II)
oxide
-
for M = Zn: white
carbonate ==> white
zinc oxide, but yellow hot
-
Many transition metal ions
(e.g. in soluble salt solutions) give hydroxide precipitates when mixed with
aqueous sodium hydroxide solution.
-
transition metal salt
solution + sodium hydroxide ==> solid hydroxide precipitate + sodium
salt
-
ionically the precipitation
reaction is : metal ion +
hydroxide ion ==> hydroxide precipitateM2+(aq)
+ 2OH-(aq) ==>
M(OH)2(s)
M can be
for the
iron(II) ion
Fe2+, pale green in aqueous solution,
-
or for the
copper(II) ion Cu2+, blue in
aqueous solution,
which gives a blue copper(II)
hydroxide precipitate
with sodium hydroxide solution.
and
the
iron(III) ion Fe3+:
Fe3+(aq)
+ 3OH-(aq) ==>
Fe(OH)3(s)
These precipitates are basically solids, but of a
somewhat gelatinous nature because they incorporate water in their
structure.
-
Also note that iron has two
valencies or combining power
giving different compound formulae.
Multiple valency, hence multiple compound formation, is another
characteristic (but not unique) feature of transition metal chemistry.
There are more details
and more tests on the
Chemical
Identification page (use the alphabetical list at the top).
(e) Catalytic Properties
- Uses of Transition Metals
(1) The metallic elements themselves
are used as catalysts
- Many transition metals are used directly as catalysts in industrial chemical processes and in the anti-pollution catalytic converters in car exhausts.
- For example iron is used in the HABER
PROCESS for the synthesis of ammonia:
- Nitrogen + Hydrogen
==>
Ammonia (via a catalyst of Fe atoms)
-
or
N2(g) + 3H2(g)
==>
2NH3(g)
- Platinum and rhodium
(in other
transition series below Sc-Zn) are used in the
catalytic converters in car exhausts to reduce the emission of carbon monoxide
and nitrogen monoxide, which are converted to the non-polluting gases nitrogen
and carbon dioxide.
- 2NO(g)
+ 2CO(g) ==> N2(g) + 2CO2(g)
- Nickel is the catalyst for
'hydrogenation' in the margarine industry. It catalyses the addition of
hydrogen to an alkene carbon=carbon double bond (>C=C< + H2 ==>
>CH-CH<). This process converts unsaturated vegetable oils into higher
melting saturated fats which are more 'spreadable' with a knife!
(2) Some compounds of transition metals
are also used as catalysts
- As well as the metals, the compounds of transition metals also acts as catalysts.
- EXAMPLES
- For example manganese dioxide (or manganese(IV) oxide),
MnO2, a black powder, readily decomposes an aqueous solution of hydrogen peroxide:
==>
water + oxygen
-
or 2H2O2(aq)
==>
2H2O(l) + O2(g)
- A useful reaction in the laboratory for
preparing oxygen gas.
Vanadium(V) oxide (vanadium pentoxide, V2O5) is used as the catalyst in converting sulphur dioxide
into sulphur trioxide as a stage in the manufacture of sulphuric acid in the
CONTACT PROCESS.
==>
2SO3(g) (via V2O5
catalyst)
A very important industrial process because sulphuric acid is a widely
used chemical in industry.
(f)
More on the Uses of Transition Metals and their compounds
Transition metals are extremely useful metals on account of their physical or chemical
properties eg lack of corrosion and greater strength compared to the Group 1
Alkali Metals. Many are used in alloys (a mixture of metal with at least one
other metallic or non-metallic substance).
For catalysts - see above. Their strength and hardness makes them very useful as
structural materials.
 IRON,
Fe
- Cast iron is used for man-hole covers because it is so hard
wearing but it is brittle due to a high carbon content.
- When alloyed with 1% carbon iron forms mild
steel which is not brittle, but is more malleable and corrosion resistant
than cast iron. Mild steel is used for
food cans, car bodies (but galvanising and several
coats of paint help it to last!) and machinery etc.
- Steel is an alloy based on iron mixed with
carbon and usually other metals added too. There are huge
number of steel 'recipes' which can be made to suit particular purposes by
changing the % carbon and adding other metals e.g. titanium steel for armour plating.
- CHROMIUM, Cr
- Chromium steel (stainless steel,
mixing and melting together Fe + Cr and maybe Ni too) with good
anti-corrosion properties, used for cutlery and chemical plant reactors.
 COPPER,
Cu
- The alloy BRASS is a mixture copper and zinc.
It is a much more hard wearing metal than copper (too soft) and zinc (too
brittle) but is more malleable than bronze for 'stamping' or 'cutting' it into
shape.
- Copper is used in electrical wiring because it is a good conductor of
electricity but for safety it is insulated by using poorly electrical conductors like PVC
plastic.
- Copper is used in domestic hot water pipes because it is relatively unreactive to water and therefore doesn't corrode easily.
- Copper is used for cooking pans because it is relatively unreactive to water and therefore doesn't corrode
easily, readily beaten or pressed into shape but strong enough, it is high
melting and a good conductor of heat.
- Copper is also used as a roof covering and weathers to a green colour as a surface
coating of a basic carbonate is formed on corrosion.
- The alloy BRONZE is a mixture of copper and
tin (Sn) and is stronger than copper and just as corrosion resistant, e.g.
used for sculptures.
- Iron and steel are used for boilers because of
their good heat conduction properties and high melting point.
- Copper compounds are used in fungicides and pesticides e.g. a traditional
recipe is copper sulphate solution plus lime is used to kill greenfly.
- Copper is alloyed with nickel to give 'cupro-nickel',
an
attractive hard wearing 'silvery' metal for coins.
- Steel, iron or copper are used for cooking pans
because they are malleable, good heat conductors and high melting.
- NICKEL is alloyed with copper to give
'cupro-nickel',
an
attractive hard wearing 'silvery' metal for coins.
 ZINC
- Zinc is used to galvanise (coat) iron or steel to sacrificially protect them from corrosion.
The zinc layer can be put on the iron/steel object by chemical (see electroplating
and below) or physically dipping it into a bath of molten zinc.
- Zinc sulphate
solution can be used as the electrolyte for electroplating/galvanising
objects with a zinc layer.
- Zinc is used as a sacrificed electrode
in a zinc-carbon battery. It slowly reacts with a weakly acidic
ammonium chloride paste, converting chemical energy into electrical
energy.
- The alloy BRASS is a mixture copper and zinc.
It is a much more hard wearing metal than copper (too soft) and zinc (too
brittle) but is more malleable than bronze for 'stamping' or 'cutting' it into
shape.
 Transition metal compounds (often oxides)
of copper, iron, chromium and cobalt are used to
pigments for artwork, and give
bright colours to stained glass
and
ceramic/pottery glazes e.g.
- Paint pigments: chromium oxide Cr2O3
green, iron oxide (haematite) Fe2O3
red-brown, manganese oxide MnO2
black, copper hydroxide-carbonates (malachite-green,
azurite-blue) and titanium dioxide TiO2
white.
- Stained glass: cobalt oxide CoO blue,
iron oxide/carbonate green,
Cu metal red, CuO turquoise.
- NICHROME is an alloy of chromium and nickel.
It has a high melting point and a high electrical resistance and so it is used
for electrical heating element wires.
-
NITINIOL: Titanium and nickel
are the main components of Nitinol 'smart' alloys which are very
useful intermetallic compounds. 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
- TUNGSTEN is used as the filament in
light bulbs because its melting point is so high.
- Transition metals like platinum and rhodium
are used as metal catalysts in the catalytic converters used in car vehicle
exhausts to reduce carbon monoxide and nitrogen oxide polluting emissions.
- Bright, shiny and relatively
unreactive
copper, silver and gold are used in jewellery.
- There is a note about the bonding in metals and
structure
of alloys on another page.
(g) What about the uses of
non-transition metals?
Note on Aluminium
- It is NOT a transition
metal !
- e.g. it does not form coloured
compounds,
it does not act as a catalyst etc.
- BUT it is high melting, of low density
and one of the most used and useful non-transition metals.
- It is rather weak BUT when alloyed with copper,
manganese and magnesium and it forms a much stronger alloy called duralumin.
- It does not readily corrode due to a
permanent Al2O3 aluminium oxide layer on the surface which does not flake off
and protects the aluminium from further oxidation.
- Because of its alloyed strength,
lightness and anti-corrosion properties it is used in aircraft
construction, window frames, hifi chassis etc.
- Its a good conductor of heat and can be
used in radiators.
- Its quite a good conductor of electricity, and
also because its light, it is used in conjunction with copper (excellent
electrical conductor) in
overhead power lines (don't want them too heavy when iced up!). The
cables however do have a steel core for strength!
- Poorly electrical conducting ceramic
materials are used to insulate the wires from the pylons and the
ground.
Other
metals and their uses
-
A mixture of tin and lead
is mixed to give the alloy SOLDER
which is a relatively low melting
solid for electrical connections. -
Tin
is an unreactive metal and is used to coat more corrodible metals like
iron-steel. A 'tin can' is actually made of steel with a fine protective
coating of tin metal over the surface of it.-
Lead is a soft, very malleable relatively unreactive metal used in
roofing. 'Flashings' are used to seal sections of roofs e.g. between walls
and the ends of layers of tiles or slates. Electrical cables can be encased
in it. It is used with lead oxide in the manufacture of electrodes of road
vehicle car batteries. Because of its high density it is used as a shield
from dangerous alpha/beta/gamma radiation from radioactive materials and
X-rays, so it is used in nuclear processing facilities etc. and
radiographers wear a lead apron when you go for an X-ray on your bones.
-
PEWTER is an alloy of
mainly tin plus small amounts of copper, bismuth (Bi) and antimony (Sb), it
is
stronger than tin but is easy to etch and engrave.
-
DENTAL AMALGAM ALLOY is
a mixture of tin, mercury and silver. When first prepared its soft and
malleable before hardening to that undesired filling! It has good
anti-corrosion properties and resists the attack of acidic products produced
by bacteria in the mouth. An
amalgam is an alloy metal compound made from a mixture of mercury and other
metals which may be liquid and set to a solid after preparation.
Links to other information
of uses of metals:
Extra Industrial
Chemistry and sodium in
Group 1 alkali Metals.
Detailed
GCE-AS-A2-IB Advanced Level Notes on the 3d block Transition Metals
Important concepts to
understand,
facts to know, information points to learn and revise when studying for exams, lesson
preparation, teaching and learning to study for yourself or students pupils
parents parental info help with revising topics homework coursework projects and
assignments in understanding science chemistry courses ~US grades 8, 9, 10
Copyright © Dr W P Brown 2000-2008 All rights reserved including the
revision notes pages, quizzes, worksheets etc
|
