8 & 9 Bonding

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8 9 Bonding
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8.1 Chemical Bonds

• Metallic
• Between metals
• Free-flow of electrons
• Ionic
• Metal Non-metal
• Electrons are transferred due to LARGE difference
  in electronegativities (?Eneg 1.7-4.0)
• Covalent
• 2 Non-metals, usually
• Electrons are shared due to small difference in
  electronegativities (?Eneg 0.0-1.6)

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8.2 Ionic Compounds

• Strong attraction between cation and anion
  causes
• Solids atoms are held closely together
• High m.p. and b.p. difficult to separate atoms
• Conductivity able to conduct heat/electricity
  in molten or aqueous state
• High Bond energies relatively large amount of
  energy stored

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Draw Lewis Dot Diagrams for the following Ionic
compounds.

• Magnesium chloride Magnesium oxide
• Calcium chloride Aluminum fluoride

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Lattice Energy

• Energy needed to separate ionic compound into
  gaseous ions
• NaBr(s) ?
• Dependent on
• Charges of cation and anion
• Larger the product of charges, larger the lattice
  E
• Ex
• Bond length (determined by ionic radii)
• - Smaller the radii, larger the lattice E
• Ex

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List the ionic compounds (MgCl2, MgO, CaCl2,
AlF3) in order of increasing lattice energy.

• What is the relevance?

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8.3 8.4 Covalent Bonds
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Polarity

• uneven sharing of electrons
• electrons are pulled toward more electronegative
  atom
• Also referred to as a dipole moment
• F-Br F-Cl F-F

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Types of Covalent Bonds

• Nonpolar covalent
• Even sharing of electrons
• ?Eneg 0.0-0.3
• Polar covalent
• Uneven sharing of electrons
• ?Eneg 0.4-1.6
• Coordinate covalent
• Electrons being shared are donated by a single
  species
• Usually with transition metals

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8.5 Lewis Dot Diagrams (that follow octet rule)

• Carbon tetrachloride Sulfur dibromide
• Ammonia Ammonium

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Multiple Bonds

• Atoms can share more than 2 e-

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Examples

• Oxygen Ethene
• Ethyne Cyanide

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8.5-8.6 Exceptions to the Octet Rule
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Incomplete Octets

• Central atom has lt 8 valence e-
• Beryllium iodide
• boron trihydride

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Expanded Octets

• Central atom must have at least 3 energy levels
• Peripheral atoms must have HIGH electronegativity
• Sulfur tetrafluoride Sulfur hexafluoride
• Xenon dioxide Phosphorus pentafluoride

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Radicals odd number of electrons present in
compounds, usually with nitrogen

• Nitrogen Monoxide
• Nitrogen Dioxide

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Formal Charge Resonance
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Identifying Formal Charge

• N2 vs. CO

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Minimizing formal charges overrides octet rule

• AsOBr3

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Phosphate v. Sulfate v. Perchlorate
(isoelectronic family)
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Nitrate and Carbonate (also isoelectronic to
each other)
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Benzene (C6H6)
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9.1-2 Molecular Shapes and VSEPR Theory
Electron Domain Molecular Geometry/Shape
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Draw LDD. Then identify electron domain and
molecular geometry.

• ICl3 SF4
• I3- XeF4

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9.2 Bond Order

• Used to compare bond energies and length
• HIGH ? high bond energy and short length
• LOW? Low bond energy and long length
• Compare C-O bond order in CO, CO2, CH3OH, and
  CO3-2

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Determine the order of the S-O bond in each of
the following. Then, list the compounds in order
of decreasing S-O bond length.

• Sulfur dioxide
• Sulfite
• Sulfate

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9.3 Polarity of Molecules

• Polar
• Contains polar bonds
• Molecule is not symmetrical so dipole moments
  dont balance out
• Examples
• CCl4 NCl3 NI3

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Intermolecular Forces(also known as Van der
Waals forces)attractive forces between molecules

• London Dispersion Force (LDF)
• caused by movement of e-, creating temporary
  dipoles

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IMFs (cont.)

• Dipole-dipole
• partial charges of polar molecules attracted to
  one another

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IMFs (cont.)

• Hydrogen bonding
• stronger version of d-d where unshielded nucleus
  of H attracted to LP of N, O, or F

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Draw LDDs for the following particles. Then
identify molecular geometry, polarity, and
strongest IMF.

• PFO
• SeCl4
• BBr3

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9.5 Hybridization

• s, p, and d orbitals blend to hold valence
  electrons

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Single Bond
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Double Bond (link to show sigma vs. pi bonding)
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Triple Bond
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Benzene (C6H6)