solidssolids adapted from a presentation by dr. schroeder, wayne state university

SolidsSolidsSolidsSolids

Adapted from a presentation by Dr. Schroeder, Wayne State University

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Properties of SolidsProperties of SolidsProperties of SolidsProperties of Solids

1. Definite shape, 1. Definite shape, definite volumedefinite volume

2. Particles are CLOSE 2. Particles are CLOSE togethertogether

3. STRONG IM forces3. STRONG IM forces

4.4. Often highly ordered, Often highly ordered,

5.5. Rigid, incompressibleRigid, incompressible

1. Definite shape, 1. Definite shape, definite volumedefinite volume

2. Particles are CLOSE 2. Particles are CLOSE togethertogether

3. STRONG IM forces3. STRONG IM forces

4.4. Often highly ordered, Often highly ordered,

5.5. Rigid, incompressibleRigid, incompressible

ZnS, zinc sulfideZnS, zinc sulfide

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SOLIDS can be arranged into two categories:

• Crystalline Solids:Crystalline Solids: have a regular structure in which particles pack in a repeating pattern from one edge of the solid to another.

• Amorphous Solids:Amorphous Solids: “solids without form” have random structure and little long-range order. Includes glass and many plastics.

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CRYSTALLINE SOLIDSCRYSTALLINE SOLIDS

• There are four types of crystalline There are four types of crystalline solidssolids

• Classified on a basis of the bonding Classified on a basis of the bonding or attractive force holding them or attractive force holding them togethertogether

1. Molecular solids

2. Covalent network solids

3. Ionic solids

4. Metallic solids

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1. Molecular Solids1. Molecular Solids

• Composed of atoms or molecules Composed of atoms or molecules held held together by IMF’stogether by IMF’s

• Relatively soft, low mp’s, bp’s, etc.Relatively soft, low mp’s, bp’s, etc.• Water, carbon dioxide, NH3, Iodine (I2), sugar

(C12H22O11), and polyethylene are typical examples.

• Example: Dry ice (CO2) sublimes at -78oC.

• Strong intramolecular (covalent) bonds• O==C==O• Weak intermolecular forces - London• O==C==O• - + -• Symmetric molecule, nonpolar

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Molecular Solids (cont.):Molecular Solids (cont.):• Example: Polyethylene

• (-CH2-CH2-)n

• Polyvinyl chloride (PVC)

• (-CH2-CHCl-)n

• or

– H Cl H Cl H Cl

– | | | | | |

– ....C---C---C---C---C---C....

– | | | | | | NONPOLAR

– H H H H H H London Forces

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2. COVALENT SOLIDS2. COVALENT SOLIDS

• Form crystals that can be viewed as a single “giant” molecule held together by an endless number of covalent bonds.

• Diamond is an example of a covalent solid. Diamond is hard and difficult to melt (mp = 3,550oC) because all bonds are equally strong. Also graphite, quartz, and asbestos.

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DiamondDiamond

GraphiteGraphite

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3. IONIC SOLIDS3. IONIC SOLIDS

• Are held together primarily by the strong force of attraction between oppositely charged ions (ionic bonds)

• Are typically hard, brittle, and nonconducting

• High mp’s and bp’s

• NaClNaCl and CsFCsF are typical examples.

• Note: the strength of the bond depends on the radii of the formative ions. That is, the bond becomes weaker as the ions become larger or the ratio changes away from 1:1

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Common Ionic SolidsCommon Ionic SolidsCommon Ionic SolidsCommon Ionic Solids

• Zinc sulfide, ZnSZinc sulfide, ZnS

• The SThe S2-2- ions are in ions are in TETRAHEDRALTETRAHEDRAL holes in the Znholes in the Zn2+2+ FCC lattice.FCC lattice.

• This gives 4 net This gives 4 net ZnZn2+2+ ions and 4 ions and 4 net Snet S2-2- ions. ions.

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4. METALLIC SOLIDS4. METALLIC SOLIDS

• Malleable and ductile• Held together by “metallic bonds”• Have their valence electrons delocalized over many metal atoms. For this reason most metals are good conductors.

– “sea of electrons” model– Jello with fruit

• Includes Au, Fe, Al, etc.

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4. METALLIC SOLIDS4. METALLIC SOLIDSAtom “core”

e-

e-

e-e-

e-

e-

e-

e-

e-

e-

Delocalized valence electrons (move around)

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Types of Crysatalline Types of Crysatalline SolidsSolids

Types of Crysatalline Types of Crysatalline SolidsSolids

TYPETYPE EXAMPLEEXAMPLE FORCEFORCE

1. Molecular Ice, I1. Molecular Ice, I22 DipoleDipole

LondonLondon

2. 2. Network DiamondNetwork Diamond ExtendedExtended Graphite Graphite covalentcovalent

3. Ionic 3. Ionic NaCl, CaFNaCl, CaF22, ZnS, ZnS Ion-ionIon-ion

4. Metallic4. Metallic Na, Fe Na, Fe MetallicMetallic

TYPETYPE EXAMPLEEXAMPLE FORCEFORCE

1. Molecular Ice, I1. Molecular Ice, I22 DipoleDipole

LondonLondon

2. 2. Network DiamondNetwork Diamond ExtendedExtended Graphite Graphite covalentcovalent

3. Ionic 3. Ionic NaCl, CaFNaCl, CaF22, ZnS, ZnS Ion-ionIon-ion

4. Metallic4. Metallic Na, Fe Na, Fe MetallicMetallic

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Amorphous SolidsAmorphous Solids

• No regular geometric patternNo regular geometric pattern

• More “jumbled up”More “jumbled up”

• Typically long chains of molecules that get Typically long chains of molecules that get tangled up togethertangled up together

• Classified on a basis of the bonding or Classified on a basis of the bonding or attractive force holding them togetherattractive force holding them together

• Held together by IMF’sHeld together by IMF’s

• Examples: waxes, asphalt, many plasticsExamples: waxes, asphalt, many plastics

solidssolids adapted from a presentation by dr. schroeder, wayne state university

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