metallic bonding intermolecular forces. basic metallic properties malleable: metals can be shaped...
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Metallic BondingMetallic BondingIntermolecular ForcesIntermolecular Forces
Basic metallic properties
Malleable: metals can be shaped into thin sheets
Ductile: metals can be drawn into wires.Metals are good conductors of electricity.
Ionic solids are brittle
Metals are good conductors of heat.
Properties of metals based on molecular structure
Metal Ion (+)
- close-packed in structure.
- each atom surrounded by 8 to 12 adjacent atoms - e- are mobilenot confined to any particular metal ion (0 electrostatic attraction)
evenly distributed
Electron-Sea Model
Crystalline Structure of a Metal
1.Body-centered Cubic:• Every atom (except those on
the surface) has 8 neighbors 2.Face-centered Cubic:• Every atom has 12 neighbors
3.Hexagonal close packed:• Every atom has 12 but
different pattern due to hexagonal
Alloy: material that contains more than 1 element and has characteristic properties of metals.
Primary method of modifying properties of pure metals
Brass (Zn & Cu) Steel (Fe & C)
Why use alloys?Why use alloys?
Properties are often superior to the pure element
Sterling silver (92.5% Ag, 7.5% Cu) is harder and more durable than pure Ag, but still soft enough to make jewelry and tableware
Steels are very important alloyscorrosion resistant, ductility, hardness,
toughness, cost
Properties are often superior to the pure element
Sterling silver (92.5% Ag, 7.5% Cu) is harder and more durable than pure Ag, but still soft enough to make jewelry and tableware
Steels are very important alloyscorrosion resistant, ductility, hardness,
toughness, cost
More about Alloys…More about Alloys…
Types? a) substitutional alloy- the atoms in
the components are about the same size
b) interstitial alloy- the atomic sizes quite different; smaller atoms fit into the spaces between larger
“Amalgam”- dental use, contains Hg
Types? a) substitutional alloy- the atoms in
the components are about the same size
b) interstitial alloy- the atomic sizes quite different; smaller atoms fit into the spaces between larger
“Amalgam”- dental use, contains Hg
Intermolecular forces are forces that exist between molecules.
contribute to properties of solids, liquids, & gases
weaker than ionic or covalent bondsEx. melting & boiling point
Intermolecular ForcesIntermolecular Forces
Types of intermolecular forces
- Ion-dipole attractions
- Dipole-dipole attractions
- Hydrogen bonding
- London dispersion forces
Ion-dipole attractions
They occur between an ion and the partial charge on the end of a polar molecule.
Dipole-dipole attractions
These forces occur when neutral polar molecule attract each others.
+ & - ends are in close proximity to each other
Weaker than ion-dipole attractions
London dispersion forces
Occur when a temporary dipole is induced on a nonpolar molecule/atom by e- from another nonpolar molecule/atom.
Ex. He(g)
Hydrogen Bonding
H-bonding is a special type of intermolecular attraction between the H atom in a polar bond and a nonbinding e- pair on a small electronegative ion or atom Typical H-bonding pairs include:
H-OH-FH-N
H-bonding in H2O causes hexagonal cavities to form in its solid state.Due to increased distance between molecules.
H2O expands when frozen
H2O is less dense when frozen