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Unformatted text preview: Chapter 8: Covalent Bonding 335 Chapter 8: Covalent Bonding Teaching for Conceptual Understanding Lewis structures are nothing more than pictorial representations of the atoms and electrons involved in bonding. (They do not indicate the geometry of the molecule.) The process of drawing Lewis structures is rule based and best taught (and learned) as an algorithm. Explain to students the importance of following the Guidelines for Writing Lewis structures found in Section 8.2. Although there are several approaches to drawing correct structures, student success will increase when a systematic set of steps is done in order. Students who are still confused by the formation of ions may miscalculate the total number of valence electrons for ions by subtracting electrons for anions and add electrons for cations. At first, it is best to draw bonding electron pairs as two dots instead of a dashed line. It reinforces the idea of sharing two electrons and it helps students better visualize all the valence electrons. Incorrect examples like Questions 21 and 22 in Questions for Review and Thought assess student understanding at a higher cognitive level. Consider using similar types of questions on quizzes and exams. Suggestions for Effective Learning Ball-and-stick models will help students visualize the differences among single, double, and triple bonds. Depending upon the models used, the shortening of bond length with increasing number of bonds may be illustrated also. Tell students that hydrogen and the halogens generally have one bond, oxygen two bonds, nitrogen three bonds, and carbon four. This information can provide them with a quick check for the Lewis structures they draw. Choose between the synonyms, nonbonding electrons and lone pair electrons. Switching between the two can be confusing for some students. The textbook uses the term lone pair electrons. Cooperative Learning Activities Questions, problems, and topics that can be used for Cooperative Learning Exercises and other group work are: Most students have been exposed to drawing Lewis structures in their high school chemistry courses. Instead of boring them with a lecture, assess their knowledge with a small group activity. Provide students with a list of the names (reinforces nomenclature) of 8 10 covalent compounds, ordered in increasing complexity of Lewis structures, then have students draw the Lewis structures. Discuss only those structures with which students have difficulties. Questions for Review and Thought from the end of this chapter: 80, 94, and 106-118 Conceptual Challenge Problems: CP8.A, CP8.B, and CP8.C Concept mapping terms: bond length, bonding electrons, covalent bonds, double bond, electronegativity, Lewis structure, lone pair electrons, nonbonding electrons, nonpolar covalent bond, octet rule, polar covalent bond, resonance structures, single bond, triple bond. covalent bond, resonance structures, single bond, triple bond....
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