Published on October 13, 2007
Chapter 9: Chapter 9 Ionic and Covalent Bonding Ionic Bonding: Ionic Bonding Electrostatic attraction of ions of opposite charge Energetics of Ionic Bonding: Energetics of Ionic Bonding Ionic Radii: Ionic Radii Comparison of Atomic and Ionic Radii: Comparison of Atomic and Ionic Radii Ionic Radii: Ionic Radii Transition Metals Ions: Transition Metals Ions Cr+3 Fe+2 Co+2 Cu+2 Mn+2 Fe+3 Ni+2 Zn+2 Shell Model of the Atom: Shell Model of the Atom G.N.Lewis 1875-1946 AmericanChemist Lewis Symbol valence shell electrons = Group A # Molecular Substances: Molecular Substances Iodoform Carbon tetrachloride Lewis Symbol: Lewis Symbol Sulfur => S Group VIA 6 valence electron . : S : . Lewis Electron Dot Symbols: Lewis Electron Dot Symbols Lewis Structures: Lewis Structures combinations of Lewis symbols which represent possible bonding Octet Rule In compound formation an atom gains or loses electrons, or shares pairs of electrons, until its valence shell has eight electrons. Covalent Bonding: Covalent Bonding sharing of electrons H:H H-H Potential Energy Curve for H2: Potential Energy Curve for H2 Lewis Structures: Lewis Structures CH4 methane Lewis Structures: Lewis Structures C2H6 ethane Multiple Covalent Bonds: Multiple Covalent Bonds double bond => 2 pairs shared triple bond => 3 pairs shared normally occurs between: C atoms; N atoms; O atoms; a C atom and a N, O or S atom a N atom and a O or S atom a S atom and an O atom Multiple Covalent Bonds: Multiple Covalent Bonds Lewis Structures: Lewis Structures CO2 carbon dioxide .. .. : O :: C :: O : Lewis Structures: Lewis Structures CO carbon monoxide : C ::: O : Exceptions to Octet Rule: Exceptions to Octet Rule NO nitric oxide .. .. .N :: O: Exceptions to Octet Rule: Exceptions to Octet Rule expanded octet PF5 .. : F : .. .. .. : F . P . F : .. .. .. .. : F : : F : .. .. Exceptions to Octet Rule: Exceptions to Octet Rule SF6 .. : F : .. .. .. : F . . F : .. .. S .. .. : F . . F : .. .. .. : F : .. Delocalized Bonding in Sodium Metal: Delocalized Bonding in Sodium Metal Linus Pauling: Linus Pauling 1901–94 American chemist One of the few recipients of two Nobel prizes. His paper “The Nature of the Chemical Bond and the Structure of Molecules and Crystals” won him the 1954 Nobel Prize in chemistry. Won the peace prize in 1962. Electronegativity: Electronegativity Pauling Scale relative attraction of an atom for electrons, its own and those of other atoms same trends as ionization energy, increases from lower left corner to the upper right corner fluorine: E.N. = 4.0 Electronegativities of the Elements: Electronegativities of the Elements Covalent Bond Properties: Covalent Bond Properties electronegativity nonpolar bonds => diff. EN = 0 polar bonds => diff. EN > 0 ionic bonds => diff. EN > 1.5 Slide30: Compare O-O and O=O. Is O=O expected to be stronger, weaker, or the same strength? Slide31: Is O=O expected to be longer, shorter, or the same length?
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