bonding in solids valentin panyushenko chris zheng
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Bonding in SolidsBonding in Solids
Valentin PanyushenkoValentin Panyushenko
Chris ZhengChris Zheng
Molecular SolidsMolecular Solids
Held together by Held together by intermolecular forcesintermolecular forces
Forces are weak; solidForces are weak; solidsoft; low melting pointssoft; low melting points
Typically gas or liquid inTypically gas or liquid inroom temperatureroom temperature
Ex. Ar, HEx. Ar, H22O, COO, CO22
Molecular SolidsMolecular Solids
Property of molecular solids depend on:Property of molecular solids depend on: Strength of the forcesStrength of the forces Abilities of molecules to pack efficiently in 3DAbilities of molecules to pack efficiently in 3D
CH3 OH
Benzene Toluene PhenolMelting point (˚C) 5 -95 43Boiling point (˚C) 80 111 182
Intermolecular ForcesIntermolecular Forces
London dispersion: weakest;London dispersion: weakest;result from attractions betweenresult from attractions betweendipolesdipoles
H Bonding: strongest; molecules H Bonding: strongest; molecules containing H bond to an electro-containing H bond to an electro-negative elementnegative element
Dipole-dipole: attraction between Dipole-dipole: attraction between the + end of one molecule and the + end of one molecule and the – end of anotherthe – end of another
Covalent-Network SolidsCovalent-Network Solids
Held together by covalent Held together by covalent bondsbonds
Compared to molecular Compared to molecular solids: harder and higher solids: harder and higher melting points melting points
In diamond:In diamond: Each C is bonded to four Each C is bonded to four
other Cother CMelting point: 3550 ˚C
Diamond
Covalent-Network SolidsCovalent-Network Solids
Graphite:Graphite: C atoms arranged in C atoms arranged in
hexagonal ringhexagonal ring Each C is bonded to three Each C is bonded to three
others in the layerothers in the layer Good conductor of Good conductor of
electricity b/c delocalized electricity b/c delocalized ππ bonds bonds
Used as lubricant and the Used as lubricant and the “lead” in pencils“lead” in pencils
Graphite
Melting point: 3652 – 3697 ˚C
Ionic SolidsIonic Solids
Ions held together by Ions held together by ionic bondsionic bonds
Strength of ionic bonds Strength of ionic bonds depend on the chargesdepend on the charges
Structure depend on Structure depend on charges and sizes of charges and sizes of ionsions
NaCl: each NaNaCl: each Na++ ion is ion is surrounded by 6 Clsurrounded by 6 Cl-- ions ions
Gray: Na. Green: Cl
Ionic Solid StructuresIonic Solid Structures ZnS: ZnZnS: Zn2+2+ ions surround ions surround
tetrahedrally by four Stetrahedrally by four S2-2- ions ions
Blue: S. Yellow: Zn
CaFCaF22: There are twice as : There are twice as
many Fmany F-- ions as Ca ions as Ca2+2+ ions ions
CsCl: each CsCsCl: each Cs++ ion is ion is surrounded by eight Clsurrounded by eight Cl-- ions ions
Gray: Ca. Green: F
Gray: Cs. Green: Cl
Metallic SolidsMetallic Solids
Consist entirely of metal Consist entirely of metal atomsatoms
Each atom has 8 or 12 Each atom has 8 or 12 adjacent atomsadjacent atoms
Bonding due to delocalized valence eBonding due to delocalized valence e--
Strength of bonding Strength of bonding ↑ as # of valence e↑ as # of valence e-- ↑ ↑ Good conductors b/c of the mobility of eGood conductors b/c of the mobility of e--
Body Center-Cubic (BCC): atoms Body Center-Cubic (BCC): atoms on each corneron each corner
Atoms: Li, Na, K, Cr, Ba, etc.Atoms: Li, Na, K, Cr, Ba, etc.
Hexagonal Close-Packed (HCP): Hexagonal Close-Packed (HCP): 3 layers – top and bottom with 7 3 layers – top and bottom with 7 e-, and middle with 3 e-e-, and middle with 3 e-
Atoms: Mg, Zn, Ti, Be, etc.Atoms: Mg, Zn, Ti, Be, etc.
Metallic Bond StructuresMetallic Bond Structures
Face-Center-Cubic (FCC): atoms Face-Center-Cubic (FCC): atoms on each corner & center of each on each corner & center of each faceface
Atoms: Al, Au, Ag, Ni, Pt, etc.Atoms: Al, Au, Ag, Ni, Pt, etc.
Additional SourcesAdditional Sources http://www.science.uwaterloo.ca/~cchieh/http://www.science.uwaterloo.ca/~cchieh/
cact/c123/intermol.htmlcact/c123/intermol.html https://edocs.uis.edu/kdung1/www/https://edocs.uis.edu/kdung1/www/
Gemini/crystal_structure_visualization.htmGemini/crystal_structure_visualization.htm http://www.elmhurst.edu/~ksagarin/color/http://www.elmhurst.edu/~ksagarin/color/
discussion6.htmldiscussion6.html http://www.ndt-ed.org/http://www.ndt-ed.org/
EducationResources/EducationResources/CommunityCollege/Materials/Structure/CommunityCollege/Materials/Structure/metallic_structures.htmmetallic_structures.htm