Lecture 36
Metallic Bonds and the Properties of Metals
Ozgur Unal
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The copper wire shown to you contain
many Cu atoms.
How do you think the Cu atoms are
arranged in this wire?
The Cu atoms form lattices.
These lattices are similar to ionic crystal lattices discussed
before.
In such a lattice, 8 to 12 other
metal atoms closely surround
each metal atom.
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Metals have at least 1 valence electron.
Metals in a lattice do not share these electrons, nor they lose
them.
Instead, within the lattice, outer energy levels of metals
overlap  Electron sea model
The electron sea model proposes that all the metal atoms in a
metallic solid contribute their valence electrons to form a sea of
electrons.
The sea of electrons surrounds the metal cations in the lattice
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The electrons in the outer energy levels are not held by any
specific atom Free to move  Delocalized electrons
Delocalized electrons  Metal cations
A metallic bond is the attraction of a metallic cation for
delocalized electrons.
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Melting and boiling points
Various uses of metals: Mercury, Tungsten
Check out Table 7.12
Malleability, ductility and durability
Malleable: Easily hammered into sheets
Ductile: Easily drawn into wires
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Thermal and electrical conductivity
Easily conduct thermal
energy
Mobile electrons easily
conduct electricity
Hardness and strength
Mobile electrons also include d orbital electrons
More delocalized electrons  more hardness and strength
This is why transition metals are harder than alkali and
alkaline earth metals.
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An alloy is a mixture of elements that has metallic
properties  Wide commercial applications
Example: Stainless steel, magnets, medals etc.
Properties of alloys are somewhat different from the
elements they contain.
Example: Steel is iron + at least one other metal.
Some properties of iron is in steel, but steel is
harder than iron.
Check out Table 7.13
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Substitutional Alloys:
Some of the atoms in the original metallic solid are replaced
by other metals of similar atomic size.
Example: Sterling silver
Interstitial Alloys:
This is formed when the small holes (interstices) in a
metallic crystal are filled with smaller atoms.
Example: Carbon steel
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Substitutional Alloy or Interstitial Alloy?
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