Metallic Compounds Metallic Bonds Metals are not ionic

Metallic Compounds

Metallic Bonds Metals are not ionic, but share several properties with ionic compounds ◦ Bonds are based on the attraction of particles with unlike charges Metals form lattices, 8 -12 other metal atoms closely surround each other

Valence Electrons Metal atoms have at least 1 valence electrons ◦ Don’t share or lose (with neighbors) Crowded lattice, metal atoms outer energy level overlap ◦ “Sea of Electrons”

Sea of Electrons Proposes that all metal atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons ◦ Surrounds the metal cation in the lattice This allows the electrons to move freely from one atom to the next ◦ Delocalized electrons – electrons that are free to move

Metallic Bond The attraction of a metallic cation for delocalized electrons

What are the physical properties of metallic solids?

Physical Properties of Metallic Solids Melting and Boiling points ◦ Melting points vary greatly and are moderately high ◦ Boiling points are moderately high, but more extreme than melting points Since cations and electrons are already mobile, this lowers the melting point

Physical Properties of Metallic Solids Malleable – hammered into sheets Ductile – drawn into wire ◦ Mobile electrons can be pushed or pulled past each other Durable (generally) ◦ Mobile cations, but strongly attracted to electrons and not easily removed

Physical Properties of Metallic Solids Conductivity Electrical ◦ Electrons move easily as part of an electrical current Thermal ◦ Electrons move heat from one place to another

Physical Properties of Metallic Solids Hardness and Strength ◦ As the number of delocalized electrons increases, the properties of hardness and strength also increase

Work with your table. Compare and Contrast the physical properties of ionic and metallic solids.

Design an Experiment You are given two unknown solids, you know one is an ionic solid and one is a metallic solid. Create a procedure with at least two different tests to determine the identity of the unknown solids. Tell me why that test will determine if the solid is ionic or metallic. (Explain your reasoning)

Alloy An alloy is a mixture of elements that has metallic properties Divided into two categories ◦ Substitutional alloys ◦ Interstitial Alloys

Alloys SUBSTITUTIONAL INTERSTITIAL Some atoms in the original metallic solid are replaced by other metals of similar atomic size ◦ Ex. Sterling Silver – silver When small holes (interstices) in a metallic lattice are filled with smaller atoms ◦ Ex. Carbon Steel – holes in atoms are replaced by copper atoms, properties of both the iron lattice are filled with carbon atoms, physical properties are changed, the carbon makes the iron stronger and less ductile

Properties of Alloys Differ from the properties of the elements they contain Differ in properties depending on how they are manufactured, or the heating and cooling process