Section 4 – pg 198 Bonding in Metals Chapter 5 Section 4 – pg 198 Bonding in Metals

Pg 199 Metals and Alloys Alloy: a mixture made of two or more elements, at least one of which is a metal Alloys are generally stronger and less reactive than the pure metals from which they are made Zinc + Copper = Brass Carbon + Iron = Steel Copper + Silver = Sterling Silver

Physical Properties of Alloys Pg 199 Physical Properties of Alloys The properties of an alloy can differ greatly from those of its individual elements May also retain many physical properties of the metals depending on how they are mixed

Chemical Properties of Alloys Pg 199 Chemical Properties of Alloys The chemical properties of an alloy are different than what it is made of IE: Iron is strong and a good material to make tools out of but it rusts so we add carbon to get steel, which is hard and does not rust Iron rusts  Steel does not

Pg 200 Metallic Bonding The properties of solid metals and their alloys can be explained by the structure of metal atoms and the bonding between those atoms Most metals have 1-3 valence electrons These are held loosely and are easily lost causing the metal atom to become positively charged

Metallic Bonding Continued Pg 200 Metallic Bonding Continued Metal atoms combine in regular patterns in which the valence electrons are free to move from atom to atom Crystalline Solids Positively charged ions are closely packed together Metallic Bond: an attraction between a positive metal ion and the many electrons surrounding it

Pg 201 Metallic Properties The “sea of electrons” model of metallic bonding helps explain the malleability, ductility, luster. High electrical conductivity, and high thermal conductivity of solid metals

Malleability and Ductility Pg 201 Malleability and Ductility Metals are malleable (can be rolled into sheets or beaten into shapes) and ductile (easily bent and pulled into thin strand or wire) because the positive ions are attracted to the loose electrons all around them rather than to the other metal ions This is also why metals bend before breaking

Luster A metals luster (shininess) is due to its valence electrons Pg 202 Luster A metals luster (shininess) is due to its valence electrons When light strikes these electrons, they absorb the light and then give it off again

Electrical Conductivity Pg 202 Electrical Conductivity Metals conduct current easily b/c the electrons in a metal can move freely among the atoms

Pg 202 Thermal Conductivity Metals conduct heat easily because of the valence electrons’ freedom of motion within a metal or metal alloy

Chapter 5 Section 4 Homework – pg 203

1A. What is an alloy?

1B. From what pure metals is stainless steel made?

1C. Compare and contrast the general properties of alloys and pure metals

2A. What is a metallic bond?

2B. Explain how metal atoms form metallic bonds 2B. Explain how metal atoms form metallic bonds. What role do the valence electrons play?

2C. Review what you learned earlier about ionic bonds 2C. Review what you learned earlier about ionic bonds. How does a metallic bond differ from an ionic bond?

3A. Name 4 properties of metals. What accounts for these properties?

3B. In a light bulb, a thin tungsten wire filament that is wound in a coil conducts electric current. Describe two properties of the metal tungsten that make it good material for the filament

3C. Why is it safer to use a nonmetal mixing spoon when cooking something on a stove?