Metallic Bonds and Metallic Properties The valence electrons of metal atoms can be modeled as a sea of electrons. The valence electrons are mobile and can drift freely from one part of the metal to another. Metallic bonds consist of the attraction between the free-floating valence electrons and the positively charged metal ions. Occur between ions of the same metal or different metals. https://www.youtube.com/watch?v=vOuFTuvf4qk

Metallic Bonding Sea of electrons - regular array of cations surrounded by its valence electrons

Metal Structure Model: Atoms form a non-rigid “crystal” structure to best use available space.

Metallic Bonds and Metallic Properties A force can change the shape of a metal. Ions and free floating electrons rearrange their structure. A metal rod can be forced through a narrow opening in a die to produce wire. a) As this occurs, the metal changes shape but remains in one piece. b) If an ionic crystal were forced through the die, it would shatter. Interpreting Diagrams What causes the ionic crystal to break apart?

Metallic Bonds and Metallic Properties 1.Metals are malleable (can be pounded into another shape). Conversely, a force can shatter an ionic crystal. A metal rod can be forced through a narrow opening in a die to produce wire. a) As this occurs, the metal changes shape but remains in one piece. b) If an ionic crystal were forced through the die, it would shatter. Interpreting Diagrams What causes the ionic crystal to break apart?

Metallic Bonds and Metallic Properties Metals are ductile — can be made into wires. A metal rod can be forced through a narrow opening in a die to produce wire. a) As this occurs, the metal changes shape but remains in one piece. b) If an ionic crystal were forced through the die, it would shatter. Interpreting Diagrams What causes the ionic crystal to break apart?

Metallic Bonds and Metallic Properties Metals can conduct an electric current as a solid. A metal rod can be forced through a narrow opening in a die to produce wire. a) As this occurs, the metal changes shape but remains in one piece. b) If an ionic crystal were forced through the die, it would shatter. Interpreting Diagrams What causes the ionic crystal to break apart?

Metal Alloys Alloys are mixtures of two or more elements, at least one of which is a metal. Alloys are important because their properties are often superior to those of the individual elements.

Metal alloys Metals melted together to make a solution (homogeneous solid!!) - 2 types Substitutional Alloy – some of the host metal atoms are replaced by other metal atoms of similar size. Interstitial Alloy – some of the holes in the closest packed metal structure are occupied by small atoms. https://www.youtube.com/watch?v=9LHDSB1n11k

Metal Alloys Substitutional Alloy: some metal atoms replaced by others of similar size. More (or less) malleable, more corrosion resistant

Metal Alloys Interstitial Alloy: Interstices (holes) in closest packed metal structure are occupied by small atoms. Harder, stronger, less ductile

Metal alloys graphics Which is a substitutional alloy? Which is an interstitial alloy?

Alloys The most important alloys today are steels because they have a wide range of useful properties, such as corrosion resistance, ductility, hardness, and toughness.

Other Important Alloys Pewter (tin, silver, antimony, bismuth) Bronze (copper and tin) (Allowed ancient people in the Bronze Age to build stronger, more durable tools) Sterling silver (silver, copper)

Alloys In 1812, Napoleon tried to invade Russia. All soldiers had shiny tin buttons. In the Siberian cold, the tin disintegrated in to a fine powder. Uniforms and boots would not stay closed.