Chapter 9 - Lewis Dot Structures, and Bond Polarity Key...

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Chapter 9 Lewis Dot Structures, and Bond Polarity Key Terms for Chapter 8,9: Valence shell Valence electron Octet rule Lewis dot structure Resonance structure Electronegativity Polar covalent bonds Lone pairs Bonding pairs Double bond Triple bond
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PART I: LEWIS DOT STRUCTURES SECTION OBJECTIVES : This section will introduce you to Lewis dot structures, a convenient method for determining how atoms are connected in molecules. When this section is complete you should be able to: 1) Define the keyterms listed 2) Know how to draw Lewis dot structures for atoms and molecules (both ionic and covalent) 3) Know what valence electrons are. 4) Know what resonance structures are.
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Lewis Bonding Theory (1916) – Electrons, particularly those of the valence shell , play a fundamental role in chemical bonding. In compounds, electrons are transferred or shared in such a way that each atom acquires an especially stable electronic configuration. Usually this is a noble gas configuration, one with eight outer shell electrons or an octet . This tendency for atoms to acquire 8 valence electrons is known as the octet rule . In some cases, electrons are transferred from one atom to another. Positive and negative ions are formed and attract each other through electrostatic forces called ionic bonds – A covalent bond is formed when a pair of electrons is shared between adjacent atoms. – The moral to the story is that in many cases atoms want 8 valence shell electrons and we will often draw structures which satisfy this requirement
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Lewis Dot Symbols Element symbol represents the core (nucleus and all but the valence electrons). Dots (or x’s) represent the valence electrons. Unpaired electrons are a potential source of chemical bonding. Paired electrons—”lone pairs”—are usually not involved in bonding. Write the Lewis symbol for C
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Lewis Dot Structures: Ionic Compounds K• K + (isoelectronic to Ar) + e- F + e - [ F ] (isoelectronic to Ne) K• + F [K] + [ F ] -
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Covalent bonds result in sharing of electrons. This is demonstrated in their Lewis dot structures: Lewis Dot Structures: Covalent Compounds H O H H O H H O H Electrons shown in red are shared. Single lines in the figure on the right represent single covalent bonds; they are synonymous with a shared electron pair.
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This note was uploaded on 04/17/2008 for the course CHEM 160 taught by Professor Thompson during the Spring '08 term at University of Nebraska Kearney.

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Chapter 9 - Lewis Dot Structures, and Bond Polarity Key...

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