Unit 2, chap 13a - BONDING Chapter 13 INTRODUCTION...

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B ONDING Chapter 13
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I NTRODUCTION Attractive forces that hold atoms together in compounds are called chemical bonds The electrons involved in bonding are usually those in the outermost (valence) shell There are two types Ionic bonds result from electrostatic attractions among ions, which are formed by the transfer of one or more electrons from one atom to another Covalent bonds result from sharing one or more electron pairs between two atoms
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I NTRODUCTION The difference in electronegativity of bonding atoms is a good indicator of the type of bonding that will occur If the difference in electronegativity is large (1.9 or greater), then the outcome will most likely be ionic If the difference in electronegativity is small (less than 1.9), then the outcome will most likely be covalent If the difference is greater than 0.2, the covalent bond is probably polar
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P AULING E LECTRONEGATIVITY V ALUES
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I NTRODUCTION Example: Calculate the ϶ E for the bonding of a sodium atom to a chlorine atom and for a hydrogen atom to a chlorine atom Na = 0.9, Cl = 3.0, and H = 2.1 on the Pauling electronegativity table For Na and Cl, ϶ E = 3.0 - 0.9 = 2.1, so the bonding is ionic For H and Cl, ϶ E = 3.0 – 2.1 = 0.9, so the bonding is polar covalent
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I NTRODUCTION Example: Determine which of the following covalent bonds is most polar S-H ϶ E = 2.5 – 2.1 = 0.4 N-H ϶ E = 3.0 – 2.1 = 0.9 O-H ϶ E = 3.5 – 2.1 = 1.4 H-H ϶ E = 2.1 – 2.1 = 0 The most polar is the O-H bond
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C OMPARISON OF I ONIC AND C OVALENT C OMPOUNDS Solids with high melting points (>400°C) Generally soluble in polar solvents, insoluble in nonpolar solvents Generally conduct electricity when dissolved Gases, liquids, or solids with low melting points (typically <300°C) Generally soluble in nonpolar solvents, insoluble in polar solvents Generally do not conduct electricity Ionic Covalent
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Lewis dot structures are a convenient bookkeeping method for tracking valence electrons Valence electrons are those that are transferred or involved in chemical bonding Elements in the same periodic group have the same Lewis dot structure L EWIS D OT S TRUCTURES
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F ORMATION OF I ONIC C OMPOUNDS An ion is an atom or group of atoms possessing a net electrical charge Ions come in two basic types Positive (+) ions or cations These atoms have lost 1 or more electrons Negative (-) ions or anions These atoms have gained 1 or more electrons
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This note was uploaded on 07/25/2011 for the course CH 301 taught by Professor Fakhreddine/lyon during the Spring '07 term at University of Texas at Austin.

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Unit 2, chap 13a - BONDING Chapter 13 INTRODUCTION...

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