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Alloys & Metallic Bonding

Explanation of how metallic bonds are formed and the usefulness of alloys
by

Maria Heininger

on 30 March 2015

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Transcript of Alloys & Metallic Bonding

Metallic bonds are formed when the
valance electrons
of a metal atom become
delocalized
or detached from the rest of the atom.
Alloys
How Metallic Bonds
are formed...

How are atoms in a metal held together?
How are metallic bonds formed?
Common Alloys
Main Points of Metallic Bonding
Why are alloys more useful than pure metals?
All metal atoms are held together through
metallic bonds
.

Metallic bonds can be between
atoms of the same metals
or between
atoms of different metals.
Valance electrons in metals are
DELOCALIZED

(free to move around & not connected to the cation)
Alloys are chemical substances where the
main component is a metal
.

However, the metal is
mixed (not bonded!)
with other elements.
Brass - 67% copper, 33% zinc

Bronze - 60% copper, 39% tin, 1% aluminum & other elements

Steel - 98% iron, 1% carbon, 1% other
Has different properties then that of the pure metal (enhances the properties)
Cheaper
Does not rust as easily
Harder to break or damage
Light weight
Stronger
Metal cations are held together via a

SEA OF ELECTRONS
.
Metals have a
crystalline structure
due to the organization of their metal cations. This is why metals are relatively hard (not easy to break).
However, metals are
flexible, malleable & ductile
because the

cations in the
sea of electrons
are able to move around and not locked into place.

Alloys
Delocalized electrons - free to move around between the stable cations
Stable cations
Sea of Electrons
Properties of Pure Metals
rust easily
very soft (malleable)
heavy
expensive
Do these sound like ideal properties for making something out of metal?
Look at the list of everyday items:

Jewelry
Cars
Buildings
Baseball bats
Kitchen appliances
While these are all made from metals, are they PURE metals?
14 karat gold - NOT PURE GOLD!

59% Gold
14% Silver
23% Copper
3.5% Zinc
0.5% Cobalt
Sterling silver - NOT PURE SILVER!

92.5% Silver
7.5% Copper
The Structure of
Pure Metals vs. Alloys
The atoms in pure metals are very
organized
, which allows them to easily
slide over one another
when a force is applied
The atoms in an alloy are
disorganized
due to the mixture of the different metals and elements. When a force is applied, the atoms are
NOT able to slide over one another
. This makes the alloy extremely strong.
How are alloys made?
Alloys can be made 2 different ways:

Melting each metal and then mixing them together.

Taking a solid piece of metal, chemically coating it with a thin layer of the second metal (callled plating) and heating until they physically combine.
Full transcript