Ch. 8 Covalent Compounds I. Bond Polarity and IMF (237

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I. Bond Polarity and IMF(237 241)

• Ch. 8 Covalent Compounds

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A. Bond Polarity

• Most bonds are a blend of ionic and covalent
  characteristics
• Difference in electronegativity determines bond
  type

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A. Bond Polarity

• Electronegativity
• Attraction an atom has for a shared pair of
  electrons
• higher e-neg atom ? ?-
• lower e-neg atom? ?
• Draw the Lewis structure for HCl label partial
  charges

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A. Bond Polarity

• Electronegativity Trend (p. 178)
• Increases up and to the right

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A. Bond Polarity

• Nonpolar Covalent Bond
• e- are shared equally
• symmetrical e- density
• usually identical atoms

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A. Bond Polarity

• Polar Covalent Bond
• e- are shared unequally
• asymmetrical e- density
• results in partial charges (dipole)

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A. Bond Polarity

• Determine bond polarity
• C O
• Ca O
• Si Cl
• H F
• N N

• PC
• Ionic
• PC
• Ionic
• NPC

• 3.44 2.55 0.89
• 3.44 1.00 2.44
• 3.16 1.90 1.26
• 3.98 2.20 1.78
• 3.04 3.04 0.00

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A. Bond Polarity

• Nonpolar
• Polar
• Ionic

View Bonding Animations.
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B. Molecular Polarity

• Polar molecule one end slightly and one end
  slightly
• Molecule with 2 poles dipolar molecule or dipole

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B. Molecular Polarity

• Shape, symmetry and bond polarity determines
  molecular polarity
• H O bond is polar and water is asymmetrical, so
  H2O is polar
• C Cl bond is polar, but CCl4 is symmetrical, so
  molecule is nonpolar

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B. Molecular Polarity

• Identify each molecule as polar or nonpolar
• SCl2
• O2
• CS2
• CF4
• CH2F2

Tetrahedral, bent ? polar Nonpolar bonds ?
nonpolar Linear ? nonpolar Tetrahedral ?
nonpolar Tetrahedral ? polar
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C. Definition of IMF

• IMF Intermolecular Forces
• Attractive forces between molecules

• Much weaker than chemical bonds within
  molecules

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D. Types of IMF
Van der Waals
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D. Types of IMF

• London Dispersion Forces

View animation online.
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D. Types of IMF

• Dipole-Dipole Forces

View animation online.
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D. Types of IMF

• Hydrogen Bonding

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E. Determining IMF

• PCl3
• polar dispersion, dipole-dipole
• CH4
• nonpolar dispersion
• HF
• H-F bond dispersion, dipole-dipole, hydrogen
  bonding

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F. Network Solids

• Substances in which all atoms are covalently
  bonded to each other
• Very stable
• Examples
• Diamonds Carbon covalently bonded to carbon
• Quartz SiO2 covalently bonded and not distinct
  molecules

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II. Ions(p. 194 200)

• Ch. 7 Ionic Bonds Properties

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A. Formula Unit
The lowest whole-number ratio of ions in an ionic
compound
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B. Ionic Bonds

• Oppositely charged ions attract, force that holds
  them together ionic bond
• Electrons are transferred from cations to anions
• Bonds formed between metals and nonmetals (or
  contain a polyatomic ion)

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B. Properties of Ionic Compounds

• Most ionic compounds are crystalline solids at
  room temp
• Ionic compounds generally have high melting
  points
• Large attractive forces result in very stable
  structures

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III. Bonding in Metals(p. 201 203)

• Ch. 7 Ionic and Metallic Bonding

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A. Metallic Character

• Metals
• Nonmetals
• Metalloids

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B. Metals

• good conductors because the valence electrons are
  able to flow freely
• Valence electrons of metals can be thought of as
• a sea of electrons
• Properties can be explained by the mobility of
  electrons in metals

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C. Metallic Bond
Metallic Bonding - Electron Sea
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D. Metallic Properties

• Properties can be explained by the mobility of
  electrons in metals
• When subjected to pressure , the cations easily
  slide past each other like a ball bearing
  immersed in oil

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E. Summary
METALLIC
e- are delocalized among metal atoms
Bond Formation
Smallest Unit
electron sea
Physical State _at_ RT
solid
Melting Point
very high