Understanding metals (12 slides) (6.2MB PPT)

Understanding metals
Why are metals used to
make these items?
Properties of metals
What property of metals is being utalised in the
images on the previous slide?
• Fishing sinker
• Cooking pot
• Electrical wires
• Bread ties
• Mirror
• Car body
Metallic bonding model
How can we explain the properties exhibited by
What do the
silver spheres
What do the
red spheres
Metals form a crystal lattice
Each metal atom loses outer shell electrons to form a positive cation
 The cations form a rigid framework:
“a lattice of cations”
“a sea of delocalised electrons”
The electrons move freely through the lattice:
Delocalised: able to move freely, not fixed to one atom
The lattice is held together
by the strong electrostatic attraction
between cations and delocalised
Metal cations pack to form crystals
They form regular geometric patterns:
body – centred cubic
co-ordination no.: 8
(Na, K, Cr, Ba)
face – centred cubic
co-ordination no.: 12
(Au, Ag, Cu, Al)
hexagonal close packing
co-ordination no.: 12
(Ti, Zn, Mg)
Explaining properties of metals
Metals are hard, with a high melting point
Due to the strong electrostatic attraction
between cations and delocalised electrons
Metals are dense
Due to the close packing of the cations in the
Metals conduct electricity
The delocalised electrons are able to move
freely through the lattice and carry
electrical charge.
Metals conduct heat
Electrons move faster when heated, they can
carry the energy through the lattice
Metals are lustrous
They are shiny when polished: the
delocalised electrons are able to
reflect light.
Metals are malleable and ductile (not brittle)
Malleable: able to be beaten into a sheet
Ductile: able to be drawn into a wire
Layers of atoms can slide past each other: the delocalised electrons can move with them to
maintain the electrostatic attraction
Explain the following properties of copper:
a) Hard
The electrostatic attraction between the metal cations and
delocalised electrons is very strong
Malleable and ductile
When layers of cations are distorted, delocalised electrons are able
to move to maintain the electrostatic attraction
Good electrical conductor
The delocalised electrons are free to move and carry charge through
the metal
lustrous when polished
The delocalised electrons reflect light
• Mixing metals can
change their properties.
There are two main
types of alloys.
• Substitutional alloys 
those made from
metals of a similar size
where the second metal
takes the place of the
first in the lattice.

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