1. The Structure of Metals
Chapter 6
Section 4

2. Objectives Describe the structure and strength of bonds in metals.
Relate the properties of metals to their structure.
Define an alloy and demonstrate how the composition of an alloy affects its properties.

3. Metallic Bonds
Metallic bond is the attraction between a metal cation and the shared electrons that surround it.
The cations in a metal form a lattice that is held in place by strong metallic bonds between the cations and the surrounding valence electrons.

4. Explaining Properties of Metals
The mobility of electrons within a metal lattice explains some of the properties of metals.
The lattice in a metal is flexible unlike a lattice that is rigid in an ionic compound.

5. Alloys
An alloy is a mixture of two or more elements, at least one of which is a metal.
Alloys have characteristic properties of metals.
Gold that is in jewelry is an alloy unless it is 24-karat gold.
Silver, Copper, Nickel, or Zinc are mixed with the gold making it harder and more resistant to wear.

6. Copper Alloys The first important alloy was bronze.
Bronze in the simplest form contains only copper and tin thus making it soft.
Mixed together in bronze, the metals are much harder and stronger than either metal alone.
Scientists can design alloys with specific properties by varying the types and amounts of elements in an alloy.

7. Copper Alloys cont.
Bronze is hard enough to be used in statues and propellers on ships.
Bronze can be used to make bells which would have a clear, loud tone for several seconds.
Brass is another copper alloy. If used in bells the sound is dull.
Brass is composed of copper and zinc.
Brass is used in musical instruments.

8. Steel Alloys
Steel is an alloy of iron that contains small amounts of carbon.
Steel is firm when the lattice is harder and stronger due to the carbon added to the iron.
Stainless Steel contains chromium not carbon. More brittle than steel.
Steel cable contains sulfur, manganese, phosphorus, silicon, and carbon.

9. Other Alloys
Aluminum is used in an alloy for airplane parts. Copper or manganese is added to have a material that is lighter in weight than steel but just as strong.
Other alloys are being used for different types of parts. Some are lighter than the aluminum and other are heavier.