WebLectures: Covalent Bonds.
Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 8: Section 4-6.
- 8.4: Resonance occurs when two possible electron configurations have an equal probability. There is no force or causal rule for an electron to be in one rather than the other orbital, so the rules of quantum mechanics state that the electron will spends time in both.
- 8.5: The octet rule states that molecules have a tendency to form chemical bonds so that eight electrons, usually the s and p electrons in the outermost energy level, surround each atom, and allows us to predict Lewis structures for many different molecules and ions. But there are always exceptions! The extremely high electronegativity in fluorine allows it to grab and hang onto more than 8 electrons at a time. As a result, fluorine will form Lewis structures in which the central atom (Fl) exceeds an octet. NO and NO2 form stable molecules with single unpaired electrons.
- 8.6: The VSEPR ( valence shell electron-pair repulsion) model allows us to predict the shapes of covalent molecules and polyatomic ions. All molecular models are based on the idea that electron pairs, whether in bonds or lone electrons, repel each other and seek to be as far as part as possible. These principles predict molecular shapes that are linear, trigonal-planar (three in the same plane), tetrahedral, trigonal-bipyramidal, or octahedral. In each case, the available electron pairs seek to be equidistant from each other.
Videos for Chapter 8: Chemical Bonds and Molecular Geometry
Review the Videos at Thinkwell Video Lessons.
- Under "Chemical Bonding: Fundamental Concepts: Resonance Structures and Formal Charge"
- Under "Molecular Geometry and Chemical Bonding Theory: Molecular Geometry and VESPER Theory"
- Valence-Shell Electron-Pair Repulsion Theory
- Molecular Shapes for Steric Numbers 2-4
- Molecular Shapes for Steric Numbers 5 & 6
- Predicting Molecular Characteristics Using VESPR Theory
Homework problems: See your Moodle assignment!
LAB #6 GUIDED INQUIRY: Using qualitative methods to differentiate covalent and ionic bonds. -- Phase II
Carry out the experiment you designed in Phase I, and collect your data in a suitable format. Perform your initial analysis and determine whether you need to repeat your experiment and/or refine your procedure.
- APGIE Investigation 6: Bonding in Solids: What’s in that Bottle?
- IGHCE Lab 19.3-4 Qualitative Analysis of Inorganic Cations and Anions
- Alternative Lab: Molecular Geometry
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