Metallic Bonds and Alloys

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Metallic Bonds and Alloys

• Chemistry I

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Definitions

• Metallic Bond Bonds created by charged metal
  cations surrounded by mobile valence electrons.
  (like cations floating around in a soup of
  electrons)
• Alloys Mixtures (not compounds) of two or more
  elements, with at least one being a metal.

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Metallic Bond
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Metallic Bond Properties

• The metallic cations floating around explain both
  the ability to bend and shape metals
  (malleability and ductility).

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Metallic Bond Properties

• Another way to think about it What would happen
  if I hit the following with a hammer

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Think About It

• Why does the metal cup dent, and the glass cup
  break?
• Answer The ability for the metallic cations to
  float in the soup of electrons (Metallic
  Bonding)
• Another way to think about it metallic cations
  are kind of like a ball pit in the McDonalds
  Playplace

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Electric Conductivity

• If an electrical current came along and pushed on
  the electrons in the soup, the electrons would
  flow like water over/through rocks in a stream
  bed. This is why metals can conduct electricity.

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Alloys

• Alloys are mixtures (not compounds) of two or
  more elements, with at least one being a metal.
• Most of the metal objects you use today are
  alloys, not pure elements.
• Alloys properties tend to be far better than the
  elements that make them up.

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Alloys

• Bronze is made of 7 parts copper, 1 part tin. It
  is stronger than copper, and more-easily shaped.

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Alloys

• Cast iron (96 Fe, 4 C) is far stronger than
  iron alone. It also is more resistant to
  rusting.
• However, cast iron is not nearly as strong as
  steel

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Alloys

• Steels consist of various compositions, which
  include iron, chromium, manganese, nickel,
  molybdenum, carbon, silicon, and much more.
• Surgical steel contains 67 Fe, 18 Cr, 12 Ni,
  and 3 Mo.
• Stainless steel contains 80.6 Fe, 18 Cr, 0.4
  C, and 1.0 Ni.

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Alloys

• Alloys are mixtures (solutions), not compounds.
• Remember mixtures can be separated physically.
• Alloys can be separated by their melting point.

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Making a Brass Penny

• Brass is the result of copper and zinc forming a
  metallic bond.
• We coated the copper penny with zinc, and then
  heated it so the zinc and copper floated
  together, forming a mixture Brass.

Copper
Zinc-Coated
Brass (Cu Zn)
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Alloys They are Everywhere

• Cars have steel frames.
• Fillings in teeth consist of mercury, silver, and
  zinc.
• The school has a steel-framed infrastructure.
• The carbides that you put on your snowmobile
  actually consist of tungsten and carbon.
• Any coins you may have with you are alloys of
  nickel, copper, tin, and aluminum.

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Your Turn

• In pairs, brainstorm up some alloys youve used
  in the last week.
• Each pair will write one on the SMART Board.