Chemical Bonding

Chemical compounds

Chemical bond: attractive force holding two or more atoms together.Ionic bond results from the transfer of electrons from a metal to a nonmetal.Covalent bond results from sharing electrons between the atoms. Usually found between nonmetals.Metallic bond attractive force holding pure metals together.Chemical Bonds, Lewis Symbols, and the Octet Rule

Ionic Compounds

Ionic Bonds: One Big Greedy Thief Dog!

Covalent Bonding

Polar Covalent Bonds: Unevenly matched, but willing to share.

Metallic Bonding

Metallic Bonds: Mellow dogs with plenty of bones to go around.

Covalent Bonding

Lewis SymbolsChemical Bonds, Lewis Symbols, and the Octet Rule

Drawing Lewis StructuresFollow Step by Step Method Total all valence electrons. [Consider Charge]Write symbols for the atoms and guess skeleton structure [ define a central atom ]. Place a pair of electrons in each bond.Complete octets of surrounding atoms. [ H = 2 only ] Place leftover electrons in pairs on the central atom.If there are not enough electrons to give the central atom an octet, look for multiple bonds by transferring electrons until each atom has eight electrons around it.

Exceptions to the Octet RuleCentral Atoms Having Less than an OctetRelatively rare.Molecules with less than an octet are typical for compounds of Groups 1A, 2A, and 3A.Most typical example is BF3, with only 6Formal charges indicate that the Lewis structure with an incomplete octet is more important than the ones with double bonds.

There are five fundamental geometries for molecular shape:Molecular Shapes: VSEPR

Figure 9.3HyperChem

e-pairsNotationName of VSEPR shapeExamples2AX2LinearHgCl2 , ZnI2 , CS2 , CO23AX3Trigonal planarBF3 , GaI3AX2ENon-linear (Bent)SO2 , SnCl24AX4TetrahedralCCl4 , CH4 , BF4-AX3E(Trigonal) PyramidalNH3 , OH3-AX2E2Non-Linear (Bent)H2O , SeCl25AX5Trigonal bipyramidalPCl5 , PF5AX4EDistorted tetrahedral (see-sawed)TeCl4 , SF4AX3E2T-ShapedClF3 , BrF3AX2E3LinearI3- , ICl2- 6AX6OctahedralSF6 , PF6-AX5ESquare PyramidalIF5 , BrF5AX4E2Square PlanarICl4- , BrF4-

Timberlake LecturePLUS*

Timberlake LecturePLUS*

Polarity

Just as electrons push away from each other, so do moleculesHBrHBr is a polar molecule: dipole-dipole forces. There are also dispersion forces between HBr molecules.CH4CH4 is nonpolar: London dispersion forces, caused by temporary dipoles.SO2SO2 is a polar molecule: dipole-dipole forces. There are also dispersion forces between SO2 molecules.

What type(s) of intermolecular forces exist between each of the following molecules?HBrHBr is a polar molecule: dipole-dipole forces. There are also dispersion forces between HBr molecules.CH4CH4 is nonpolar: dispersion forces.SO2SO2 is a polar molecule: dipole-dipole forces. There are also dispersion forces between SO2 molecules.Intermolecular Forces

Intermolecular ForcesHydrogen BondThe hydrogen bond is a special dipole-dipole interaction between they hydrogen atom in a polar N-H, O-H, or F-H bond and an electronegative O, N, or F atom.A & B are N, O, or F

Intermolecular ForcesDispersion ForcesAttractive forces that arise as a result of temporary dipoles induced in atoms or moleculesion-induced dipole interactiondipole-induced dipole interaction

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