chap08notes - AP Chemistry A. Allan Chapter 8 Notes -...

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AP Chemistry A. Allan Chapter 8 Notes - Bonding: General Concepts 8.1 Types of Chemical Bonds A. Ionic Bonding 1. Electrons are transferred 2. Metals react with nonmetals 3. Ions paired have lower energy (greater stability) than separated ions B. Coulomb's Law 1. = - r Q Q E nm J x 2 1 19 10 31 . 2 a. E = energy in joules b. Q 1 and Q 2 are numerical ion charges c. r = distance between ion center in nanometers d. negative sign indicates an attractive force C. Bond Length (covalent) 1. Distance at which the system energy is at a minimum 2. Forces at work a. Attractive forces (proton - electron) b. Repulsive forces (electron - electron, proton - proton) 3. Energy is given off (bond energy) when two atoms achieve greater stability together than apart D. Covalent Bonds 1. Electrons are shared by nuclei 2. Pure covalent (non-polar covalent) a. Electrons are shared evenly 3. Polar covalent bonds a. Electrons are shared unequally b. Atoms end up with fractional charges (1) δ + or δ - 8.2 Electronegativity A. Electronegativity 1. The ability of an atom in a molecule to attract shared electrons to itself B. Electronegativity Trends 1. Electronegativity generally increases across a period (why?) 2. Electronegativity generally decrease within a family (why?) C. Characterizing bonds 1. Greater electronegativity difference between two elements means less covalent character and greater ionic character 2. We will not use the subtraction of electronegativities to determine ionic character. This text uses a practical definition to identify ionic compounds: Any compound that conducts an electric current when melted is an ionic compound.
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8.3 Bond Polarity and Dipole Moments A. Dipolar Molecules 1. Molecules with a somewhat negative end and a somewhat positive end (a dipole moment) 2. Molecules with preferential orientation in an electric field + + + - - - 3. All diatomic molecules with a polar covalent bond are dipolar B. Molecules with Polar Bonds but no Dipole Moment 1. Linear, radial or tetrahedral symmetry of charge distribution a. CO 2 - linear b. CCl 4 - tetrahedral 2. See table 8.2 in your text 8.4 Ions: Electron Configurations and Sizes A. Bonding and Noble Gas Electron Configurations 1. Ionic bonds a. Electrons are transferred until each species attains a noble gas electron configuration 2. Covalent bonds a. Electrons are shared in order to complete the valence configurations of both atoms B. Predicting Formulas of Ionic Compounds 1. Placement of elements on the periodic table suggests how many electrons are lost or gained to achieve a noble-gas configuration a. Group I loses one electron, Group II loses two, Group VI gains two, Group VII gains one…. 2. Formulas for compounds are balanced so that the total positive ionic
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This note was uploaded on 09/28/2009 for the course CHEM 102 taught by Professor Freeman during the Spring '08 term at South Carolina.

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chap08notes - AP Chemistry A. Allan Chapter 8 Notes -...

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