Zumd08 - Zumdahls Chapter 8 Chemical Bonding: Stealing and...

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Zumdahl’s Chapter 8 Chemical Bonding: Stealing and Sharing of electrons
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Chapter Contents Types of Bonds Electronegativity Ions Binary Ionic Compounds Polar Covalency The Covalent Bond Bond Energies G.N. Lewis Structures Octet or not Octet Resonance fudge Valence Shell Electron Pair Repulsion Theory
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Types of Chemical Bonds Ionic Bonds Large differences in electronegativity hold atoms together by Coulombic potentials. Radically polar poorly-shared binding electrons Covalent Bonds Near equally-shared, weakly polar binding pair Dative Bonds (donor-receptor model) Metal Bonding (macroscopic wavefunction)
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Electronegativity, χ Measure of ionization potential and electron affinity. The power to hold and attract. Empirically, deviation of bond energies, D HX , from the geometrical average of D HH and D XX . 2200 ∆χ = | χ A χ B | determines ionicity of AB 2200 ∆χ < ~1 “covalent” while ∆χ > ~2 “ionic” “Polar covalent” for ∆χ between 1 and 2. Not yet ionic, but still significantly polar.
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Pauling’s Definition D AB = [ D AA × D BB ] ½ + 96.5( ∆χ H 2.1 Pauling Electronegativities He Li 1.0 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Ne Na 0.9 Mg 1.2 Al 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0 Ar soon K 0.8 Ca 1.0 Ga 1.6 Ge 1.8 As 2.0 Se 2.4 Br 2.8 Kr 3.0 Rb 0.8 Sr 1.0 In 1.7 Sn 1.8 Sb 1.9 Te 2.1 I 2.5 Xe 2.7 Cs 0.7 Ba 0.9 Tl 1.8 Pb 1.9 Bi 1.9 Po 2.0 At 2.2 Rn
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Dipole Moment, μ 2200 ∆χ 0 implies charge separation in bonds. Charge separation means bond polarity: Product of Q times R AB , bond distance. Molecular dipole is vector sum of bond dipoles. Symmetries cause vector cancellations! Bond polarity is necessary but not sufficient cause of molecular polarity.
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Ions Electron configuration follows removal of electrons with highest n from parent atom. Effective charge governs size of ion: Cations are much smaller than parent atom. Anions are much larger but High charge anions are unstable except in compounds because 2 nd extra electron is repelled by 1 st anion’s negative charge.
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Recipe for a Crystal Gasify both the electropositive and the electronegative elements. ( H phase ) Dissociate both to atoms. ( D XX ) Condense the crystal from the infinitely remote ions. ( U lattice ) Add + and – components H formation
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This note was uploaded on 02/04/2011 for the course CHEM 102 taught by Professor Peterpastos during the Fall '08 term at CUNY Hunter.

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Zumd08 - Zumdahls Chapter 8 Chemical Bonding: Stealing and...

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