Transition Metals - Montgomery High School, Blackpool

Report
KS4 Chemistry
Transition Metals
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Contents
Transition Metals
Introducing transition metals
Physical properties
Chemical properties
Uses
Summary activities
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The transition metals
Transition metals are located in the periodic table between
group 2 and group 3. ‘Transition’ means ‘in-between’.
H 2
Li Be
Na Mg
3
transition metals
He
B C N O F Ne
Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ? ? ? ? ? ? ?
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Common transition metals
There are over 30 transition metals, but many are rare and
have few uses. What are some of the most important and
well-known transition metals?
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titanium
chromium
iron
nickel
copper
silver
platinum
gold
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Transition metal ions
All transition metals lose electrons when they react, and so
form positive ions.
Some transition metals
only make one type of
ion, for example:
 silver only forms Ag+ ions;
 zinc only forms Zn2+ ions.
However, most transition metals can form more than one type
of ion. They have variable valency. For example:
Metal
copper
iron
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Ion
Cu+
Example of compound
copper (I) oxide – Cu2O
Cu2+
Fe2+
copper (II) oxide – CuO
iron (II) chloride – FeCl2
Fe3+
iron (III) chloride – FeCl3
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Contents
Transition Metals
Introducing transition metals
Physical properties
Chemical properties
Uses
Summary activities
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General properties
The transition metals are often referred to as ‘typical’ metals
because they have properties that most people associate with
‘common’ metals.
Transition metals:
 are hard, strong and have a high density;
 are malleable and ductile;
 are lustrous;
 have high melting and boiling points (except mercury,
which is liquid at room temperature);
 are good conductors of heat and electricity.
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Density of transition metals
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Melting point of transition metals
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Comparison with alkali metals
How do the properties of transition metals compare with
those of alkali metals?
Transition metals:
 are more dense – this means that, in a fixed volume of
metal (e.g. 1 cm3), there are more atoms of a transition
metal than of an alkali metal;
 have higher melting and boiling points – except mercury;
 are harder and stronger – they are not brittle and cannot be
cut with a knife.
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True or false?
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Contents
Transition Metals
Introducing transition metals
Physical properties
Chemical properties
Uses
Summary activities
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Reactivity of transition metals
Transition metals are less reactive than alkali metals.
They tend to react relatively slowly, for example with air
and water (except iron) and acid.
The general trend is for reduced reactivity across periods.
There are exceptions, such as zinc being more reactive than
might be expected.
Sc Ti V Cr Mn Fe Co Ni Cu Zn
decrease in reactivity
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Rusting
Rusting is an oxidation reaction between iron, oxygen and
water. It is a type of corrosion.
What are the word and
chemical equations for
the formation of rust?
hydrated iron (III) oxide

(rust)
iron
+
oxygen
+
water
4Fe (s)
+
3O2 (g)
+
2H2O (g)  2Fe2O3.H2O
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Transition metals and colour
How do transition metals compare to alkali metals?
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Colour and transition metals
Most transition metals form coloured compounds.
For example:
 iron (II) compounds are usually green
e.g. iron (II) chloride (FeCl2)
 iron (III) compounds are usually
orange/brown
e.g. iron (III) oxide (Fe2O3) –
when hydrated this is rust
 copper (II) compounds are blue
e.g. copper (II) sulfate
(CuSO4.H2O) – these can be
turned white by heating the
crystals to remove the water.
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Uses of coloured compounds
Coloured compounds of transition metals are used in many
ways. For example:
stained glass windows
 paints
 glazes on pottery
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Thermal decomposition
Compounds of transition metals can be broken down into
simpler substances by heating them. This is called thermal
decomposition.
For example, carbonates of transition metals are broken
down into metal oxides and carbon dioxide when heated.
The reactants and products are different colours.
iron (II)
carbonate

heat
FeCO3 (s)

iron oxide
+
carbon dioxide
FeO (s)
+
CO2 (g)
How can the presence of carbon dioxide be tested?
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Thermal decomposition equations
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Identifying transition metal ions
The presence of transition metal ions in a solution can be
tested by adding sodium hydroxide solution.
If they are present, a metal hydroxide is formed. This is
insoluble so it appears as a solid called a precipitate.
Different metal ions produce different coloured precipitates.
For example:
 Fe2+ ions produce a grey/green precipitate of Fe(OH)2
 Fe3+ ions produce an orange/brown precipitate of Fe(OH)3
 Cu2+ ions produce a blue precipitate of Cu(OH)2
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Contents
Transition Metals
Introducing transition metals
Physical properties
Chemical properties
Uses
Summary activities
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Uses of iron
Transition metals have many uses, and these are directly
related to their physical properties.
Iron is hard, strong, abundant
and not too expensive.
It is therefore used in
construction and engineering,
but it is usually turned into
steel first.
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Uses of titanium
Titanium is as strong as steel but much lighter, and is very
resistant to corrosion.
Alloys of titanium are used
in the aerospace industry,
and in artificial joints, such
as hip ball and sockets.
Titanium dioxide is a brilliantly white compound used in
paints, plastics, paper and toothpaste.
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Uses of copper
Copper is used in wires and cables because of its good
electrical conductivity, and used in plumbing because it is
unreactive with water.
Copper is also used as a roofing material. The copper reacts
slowly with gases and water in the air to create a thin green
layer of copper compounds. This prevents the rest of the
copper from reacting.
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Alloys
Transition metals are often mixed with other metals or
non-metals to form alloys. This changes the property of the
metal so it is better suited for a particular purpose.
 Steel is an alloy of iron and other elements, such as
carbon, nickel, manganese and chromium. There are
many different types of steel, each with different properties.
 Brass is an alloy of 70% copper and 30% zinc.
 Bronze is an alloy of 90% copper and 10% tin.
 Cupronickel is an alloy of 75% copper and 25% nickel
– it is used in ‘silver’ coins.
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Catalysts
Many transition metals and their compounds are used as
catalysts.
A catalyst is a substance that speeds up a chemical reaction
without being used up.
Catalysts are very important because they can save time,
energy and money.
 Nickel is a catalyst in the production of
margarine (hydrogenation of vegetable oils).
 Iron is a catalyst in the production of
ammonia from nitrogen and hydrogen (the
Haber process).
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Catalysts – more examples
What are other examples of transition metal catalysts?
 Platinum is a catalyst in catalytic converters to reduce
levels of polluting gases. It speeds up the conversion of
carbon monoxide and nitrogen oxide to carbon dioxide
and nitrogen.
 Titanium is a catalyst in the production
of plastics.
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Pairing metals with their uses
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Contents
Transition Metals
Introducing transition metals
Physical properties
Chemical properties
Uses
Summary activities
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Glossary (part 1)
 alloy – A material containing two or more metals, or a metal
and a non-metal.
 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
electrochemical reaction such as rusting.
 density – A measure of mass in a given volume. Often
expressed in g/dm3.
 ductile – Capable of being drawn out into a wire.
 lustrous – Bright and shiny.
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Glossary (part 2)
 malleable – Capable of being bent and pressed into a
different shape.
 precipitate – A solid that forms in a solution by 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.
 valency – The number of electrons an atom must gain or
lose to obtain a full outer shell.
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Anagrams
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Reactivity and compounds
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Properties of transition metals
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Multiple-choice quiz
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