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1 of 19 © Boardworks Ltd 2016 Properties of Metals and Alloys
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Properties of Metals and Alloys
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Properties of Metals and Alloys
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What is the structure of metals?
sea of electrons
metal ions
Metal particles are held together by
strong metallic bonds and are
arranged in tightly packed layers,
forming a regular lattice structure.
The outer electrons of the metal
atoms are detached and create a
‘sea of electrons’.
These electrons are delocalised
and are free to move through
the structure. The metal atoms
become positively charged ions and
are attracted to the sea of electrons.
This strong attraction is known as
metallic bonding.
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Metallic structures
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Properties of Metals and Alloys
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Electrons and metallic bonding
How does the sea of electrons affect the properties of metals?
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Why do metals have high melting points?
Metals often have high
melting points and boiling
points. Gold, for example, has
a melting point of 1064 °C and
a boiling point of 2807 °C.
The properties of metals are related to their structure.
In metal extraction and other industrial processes, furnaces
often run continuously to maintain the high temperatures
needed to work with molten metals.
This is due to the strong
attraction between the
positively-charged metal ions
and the sea of electrons.
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How do metals conduct heat?
Delocalised electrons in metallic bonding allow metals to
conduct heat.
This makes heat transfer in
metals very efficient.
When a metal is heated, the
delocalised electrons gain
kinetic energy.
These electrons then move faster
and so transfer the gained energy
throughout the metal.
heat
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How do metals conduct electricity?
Delocalised electrons in metallic bonding also allow metals
to conduct electricity.
electricity
The delocalised electrons are
free to move through the
metal structure.
When a voltage is applied, the
electrons flow through the metal
and ‘carry’ electric charge.
Electrical conductivity relies on
mobile charge. Therefore metals are
good conductors of electricity.
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Metals are usually strong and not brittle. When a force is
applied to a metal, the layers of metal ions are able to slide
over each other, and so the structure does not shatter.
Why are metals strong?
The metallic bonds do not break because the delocalised
electrons are free to move throughout the structure.
metal after it is hit
forceforce
This also explains why metals are malleable (easy to shape)
and ductile (can be drawn into wires).
metal before it is hit
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Properties of Metals and Alloys
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What is an alloy?
An alloy is a mixture containing one or more metal elements.
The final alloy may have
very different properties
to the original metal.
By changing the amount
of each element in an
alloy, material scientists
can custom-make alloys
to fit a given job.
Steel is a common example of an alloy. It contains iron mixed
with carbon and other elements. Adding other elements to a
metal changes its structure and so changes its properties.
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Iron and steel
Iron can be extracted from its ore in a blast furnace. The
extracted iron is too soft for many uses and so it is mixed with
other elements to make alloys, which are harder.
Steel is a lot stronger and
harder than pure iron and
is a very useful material.
The extracted iron is
normally used to
make steel.
It can be used to make many things, from saucepans to
suspension bridges.
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Why is steel stronger than iron?
When other elements are added
to iron to make steel, their atoms
distort the regular structure of
the iron atoms.
The atoms in pure iron are
arranged in densely-packed layers.
These layers can slide over each
other, making pure iron a very
soft material.
This makes it more difficult for
the layers of iron atoms to slide
over each other, making the alloy
stronger than pure iron.
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Using metals and alloys
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Properties of Metals and Alloys
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Glossary
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Metallic bonding
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Multiple-choice quiz
