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Bonding in Solids

Bonding in Solids. Valentin Panyushenko Chris Zheng. Molecular Solids. Held together by intermolecular forces Forces are weak; solid soft; low melting points Typically gas or liquid in room temperature Ex. Ar, H 2 O, CO 2. Benzene Toluene Phenol

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Bonding in Solids

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  1. Bonding in Solids Valentin Panyushenko Chris Zheng

  2. Molecular Solids • Held together by intermolecular forces • Forces are weak; solidsoft; low melting points • Typically gas or liquid inroom temperature • Ex. Ar, H2O, CO2

  3. Benzene Toluene Phenol Melting point (˚C) 5 -95 43 Boiling point (˚C) 80 111 182 CH3 OH Molecular Solids • Property of molecular solids depend on: • Strength of the forces • Abilities of molecules to pack efficiently in 3D

  4. Intermolecular Forces • London dispersion: weakest;result from attractions betweendipoles • Dipole-dipole: attraction between the + end of one molecule and the – end of another • H Bonding: strongest; molecules containing H bond to an electro-negative element

  5. Diamond Melting point: 3550 ˚C Covalent-Network Solids • Held together by covalent bonds • Compared to molecular solids: harder and higher melting points • In diamond: • Each C is bonded to four other C

  6. Graphite Melting point: 3652 – 3697 ˚C Covalent-Network Solids • Graphite: • C atoms arranged in hexagonal ring • Each C is bonded to three others in the layer • Good conductor of electricity b/c delocalized π bonds • Used as lubricant and the “lead” in pencils

  7. Gray: Na. Green: Cl Ionic Solids • Ions held together by ionic bonds • Strength of ionic bonds depend on the charges • Structure depend on charges and sizes of ions • NaCl: each Na+ ion is surrounded by 6 Cl- ions

  8. Blue: S. Yellow: Zn Gray: Ca. Green: F Gray: Cs. Green: Cl Ionic Solid Structures • ZnS: Zn2+ ions surround tetrahedrally by four S2- ions • CaF2: There are twice as many F- ions as Ca2+ ions • CsCl: each Cs+ ion is surrounded by eight Cl- ions

  9. Metallic Solids • Consist entirely of metal atoms • Each atom has 8 or 12 adjacent atoms • Bonding due to delocalized valence e- • Strength of bonding ↑ as # of valence e- ↑ • Good conductors b/c of the mobility of e-

  10. Face-Center-Cubic (FCC): atoms on each corner & center of each face • Atoms: Al, Au, Ag, Ni, Pt, etc. • Hexagonal Close-Packed (HCP): 3 layers – top and bottom with 7 e-, and middle with 3 e- • Atoms: Mg, Zn, Ti, Be, etc. Metallic Bond Structures • Body Center-Cubic (BCC): atoms on each corner • Atoms: Li, Na, K, Cr, Ba, etc.

  11. Additional Sources • http://www.science.uwaterloo.ca/~cchieh/cact/c123/intermol.html • https://edocs.uis.edu/kdung1/www/Gemini/crystal_structure_visualization.htm • http://www.elmhurst.edu/~ksagarin/color/discussion6.html • http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Structure/metallic_structures.htm

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