I. Metallic Bonds How atoms are held together in the solid form. Metals hold onto their valence electrons very weakly. Think of them as positive.

I. Metallic BondsI. Metallic Bonds

How atoms are held together in the solid How atoms are held together in the solid form.form.

Metals hold onto their valence electrons Metals hold onto their valence electrons very weakly.very weakly.

Think of them as positive ions floating in a Think of them as positive ions floating in a sea of electrons.sea of electrons.

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Sea of ElectronsSea of Electrons

+ + + ++ + + +

+ + + +

Electrons are free to move through the solid.Electrons are free to move through the solid. Metals conduct electricity.Metals conduct electricity.

Metals are MalleableMetals are Malleable

Hammered into shape (bend).Hammered into shape (bend). Ductile - drawn into wires.Ductile - drawn into wires.

MalleableMalleable

+ + + ++ + + +

+ + + +

MalleableMalleable

+ + + +

+ + + ++ + + +

Electrons allow atoms to slide by.Electrons allow atoms to slide by.

ALLOYSALLOYS

Alloys are Alloys are solid solutionssolid solutions made by made by dissolving metals in other metals. They dissolving metals in other metals. They are prepared by melting the metals are prepared by melting the metals together and cooling the mixture.together and cooling the mixture.

The properties of alloys differ from those The properties of alloys differ from those of their component metals. For example of their component metals. For example stainless steelstainless steel, an alloy of iron, carbon, , an alloy of iron, carbon, chromium and nickel is stronger than iron chromium and nickel is stronger than iron and more resistant to corrosion. and more resistant to corrosion.

Name of Alloy CompositionName of Alloy Composition

________________________________________________________________________________

Sterling silver silver, copperSterling silver silver, copper

Brass copper, zinc, tinBrass copper, zinc, tin

Cast iron iron, carbonCast iron iron, carbon

Steel iron, carbonSteel iron, carbon

Stainless steel iron, chromium, carbon, nickleStainless steel iron, chromium, carbon, nickle

18 Carat gold gold, silver, copper18 Carat gold gold, silver, copper

Pewter tin, copper, bismuth, antimonyPewter tin, copper, bismuth, antimony

Plumber’s solder lead, tin Plumber’s solder lead, tin

ALLOYALLOY

A combination of 2 metalsA combination of 2 metals

IV.IV. Metallic Bonds – Properties of MetalsMetallic Bonds – Properties of MetalsA.A. Metallic BondsMetallic Bonds

1. valence electrons are 1. valence electrons are delocalizeddelocalized a. free to move from atom to atoma. free to move from atom to atom 2. bond is formed by the attraction of2. bond is formed by the attraction of metal cations for the moving electronsmetal cations for the moving electrons 3. 3. ““electron sea model”electron sea model” –atoms of –atoms of metals contribute a “sea” of free metals contribute a “sea” of free moving electrons that move from one moving electrons that move from one atom to anotheratom to another

Electron Sea Model for Metallic BondsElectron Sea Model for Metallic Bonds

Positive Ions Surrounded by Delocalized ElectronsPositive Ions Surrounded by Delocalized Electrons

B.B. Properties of MetalsProperties of Metals 1. moderately high melting points1. moderately high melting points 2. high boiling points2. high boiling points 3. 3. malleablemalleable a. can be hammered into sheetsa. can be hammered into sheets 4. 4. ductileductile a. can be drawn into wirea. can be drawn into wire 5. good conductors of heat and electricity5. good conductors of heat and electricity 6. 6. lusterluster (good reflectors of light)(good reflectors of light) 7. hardness and strength varies7. hardness and strength varies a. greater in transition elementsa. greater in transition elements

C. AlloysC. Alloys

1. mixture of two or more elements with1. mixture of two or more elements with

metallic propertiesmetallic properties

2. types2. types

a. a. substitutionalsubstitutional – atoms of similar– atoms of similar

size (sterling silver, brass, pewter)size (sterling silver, brass, pewter)

b. b. interstitialinterstitial – small holes in the – small holes in the

crystal filled with smaller atomscrystal filled with smaller atoms

(carbon steel) (carbon steel)

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