Bonding in Metals Notes 5-4

1
Bonding in MetalsNotes 5-4

• Key Ideas
• 1. How do the properties of metals and alloys
  compare?
• 2. How do metal atoms combine?
• 3. How does metallic bonding result in useful
  properties of metals?

2
Metals and Alloys

• An alloy is a mixture made of two or more
  elements, at least one of which is a metal. They
  are generally stronger and less reactive than the
  pure metals from which they are made.
• Physical Properties
• Pure gold shiny and soft
• Gold alloys still shiny but much harder (mixed
  with copper or silver)
• Chemical Properties
• Pure iron rusts when exposed to air and water
• Iron alloy stronger, resists rust (mixed with
  one or more other elements to make steel)
• Are hard, brittle crystals a characteristic
  that results from a metallic bond?
• No!!!

3
Metallic Bonding and Metallic Properties

• Bonds
• Metal atoms combine in regular patterns in which
  the valence electrons are free to move from atom
  to atom (think of metal atoms floating in a sea
  of electrons).
• Each metal ion is held in place by a metallic
  bond - an attraction between a positive metal ion
  and the many electrons surrounding it. (The more
  valence electrons, the stronger the bond.)
• 5 Properties
• Malleability easily rolled into sheets or made
  into complex shapes
• Ductility easily bent or pulled into wires
• Luster shiny and reflective
• Electrical Conductivity conduct electricity
  easily (because electrons move freely)
• Thermal Conductivity conduct heat easily
  (because electrons move freely)