11

METALS

Bonds and Properties

Alloys

Pure Elements

22

Some Properties of MetalsSome Properties of Metals

Low (lowest: Fr)Low (lowest: Fr)ELECTRONEGATIVITY

Low (lowest: Fr)Low (lowest: Fr)IONIZATION ENERGY

Lose eLose e-- to form (+) ions to form (+) ionsIon FORMATION

Solid (except Hg)Solid (except Hg)PHASE at STP

Good to ExcellentGood to ExcellentCONDUCTIVITY :

HEAT AND ELECTRICITY

Malleable & DuctileMalleable & DuctileDEFORMABILITY

HIGHHIGHLUSTER

33

Many metals have high luster

Hmmm….

How much is thisshiney Gold worth !?

400 ounces (27.5lbs)$1660.00 / ounce$664,000.00 per bar

12 bars =$7,968,000.00

44

Many Metals have high melting points

55

Metallic bonding: different from ionic bond

Both bond types due to: electrostatic attraction

Ionic bond: transfer electrons from one atom to another

Metal bonds: valence electrons ROAM FREELY from one metal atom to next

•sea of mobile electrons•accounts for properties of metals

Metal bondingMetal bonding

66Why can electrons in metals roam freely about?

77

Metal bondingMetal bonding

Metals: form organized lattice structures similar to ionic cmpdsadjacent atoms in metal lattice are all same close proximity of atoms allows outer electron

energy levels to overlap

So…

88

electrons in outer valence shell can move freely through these overlapping energy levels = “sea of mobile electrons”

99

Na 3s1 Na 3s1

overlapping valence electron orbitals

1010

Metal bondingMetal bonding

Freely moving electrons: called “delocalized” electrons allows (+) metal cation to form

Delocalized electrons move freely

throughout metal from one cation to nextcreates what’s called “the sea of mobile

electrons”

1111

This sea of electrons:• binds each metal cation to each neighbor’s cation • this creates the metal bond

1212

Metal PropertiesMetal Propertiessea of mobile electrons

givesmetals some unique

properties

since electrons move freelyfrom place to place they:● conduct electricity (flow of electrons)● conduct heatAccounts for metals being● malleable and ductile● and having luster

How do electrons do this?

1313

Electrical Conductivity

-

Free flow of electrons through the metal

+

e-e-

Flow of electrons

e- flow from metal through metal wire towards (+) charge; then flow from (-) terminal back into metal

1414

Malleability Malleability Metals & non-metals behave very differently when hit with a force such as hammer

Metals DEFORM whileNon-metals SHATTER

Why?

Metals have free flowing electrons & nonmetals do not!

1515

If apply force to metal: •metal atoms shift away from force & free electrons bond newly overlapping metal ions together•metal is deformed but shift doesn't change metal atoms

If apply force to non-metal: •like charges align (+) to (+) (-) to (-) which results in shattering due to repulsion

Metal

Non-Metal

1616

Deformation of MetalsDeformation of Metals

Deformation of MetalsDeformation of Metals

1717

As # of electrons that can be delocalized ↑ so does: Hardness and Strength

Na has one valence electron that can be delocalized so: - is relatively soft ( can be cut with a butter knife)

Mg has two valence electrons that can be delocalized so:- can still be cut but is much harder than Na

Transition metals have varied # of e-'s that can be delocalized- Chromium (Cr+6) is very hard and has high strength

1818

AlloysAlloys

mixture of elements that have metallic mixture of elements that have metallic propertiesproperties

mixture can be adjusted to get desired mixture can be adjusted to get desired propertiesproperties

substitutional and interstitial alloy (depends substitutional and interstitial alloy (depends on sizes of elements – same or different size)on sizes of elements – same or different size)

1919

Common alloysCommon alloysBrass: Cu & ZnBrass: Cu & ZnBronze: Cu, Sn & AlBronze: Cu, Sn & AlPewter: Sn, Pb & CuPewter: Sn, Pb & CuSolder: Pb & SnSolder: Pb & SnRose gold: Cu & AlRose gold: Cu & AlWhite gold: Au & Ni, Pd or PtWhite gold: Au & Ni, Pd or PtSterling silver: Ag & CuSterling silver: Ag & CuSteel: C & FeSteel: C & Fe

Stainless steel: Cr & NiStainless steel: Cr & Ni