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Schedule to Exam 2

Date Day Topics
9/22MonChapter 13... Ionic and Covalent bonding. Valence electrons. Electronegativity. Dipoles. Also covered Coulomb's Law and Bond energies. Also reminded that true chemical bonding is really a combination of covalent and ionic - we refer to each as the "character" of the bond. Most metal-to-nonmetal bonds are 80% or higher in ionic character... which does leave a smaller percentage as covalent. The reverse of this trend is for typical nonmetal-to-nonmetal bonds which are 80% or higher in covalent character. All of these ranges are measured via dipole moments. Dipoles are measured in debye units.... once again, a RANGE of value are found and one end is covalent in character and the other end ionic in character. We also saw how to depict partial positive and negative charge with the proper symbol (δ+ or δ-).
9/24WedMore on electron dot structures. Showed how to depict ionic compounds with an electron dot formula. Covered lattice energies (also called lattice enthalpies). Showed some covalent compound electron dot formulas. Announced that there is no class this Friday.
9/26FriNO CLASS TODAY!
9/29MonH06 due at 10:59 AM
Went over lattice energies some more. Showed the Born-Haber cycle in the book (fig 13.8 for LiF, fig 13.10 for MgO and NaF). Also more on average bond energies - see Table 13.6 on p 608. See example 13.5 on page 609 to see HOW to use those bond energies.
10/1WedA reminder (with iclickers) that you DO need to know your nomenclature of polyatomic ions. Did more electron dot/line formulas. Defined what bond order is. Used nitrate as a great example of resonance structures. Each resonance structure of a species contributes to the overall representation of the structure. In the case of nitrate, the 3 resonance structures each have the double bond in a different spot. The average of these structures gives a bond order of 1.33 for the three N-O bonds which matches what we find experimentally.
10/2ThurH07 due at 11:15 PM (night time)
10/3FriFinished up electron dot stuff - did some examples: sulfate, xenon trioxide, and triiodide. Valence Shell Electron Pair Repulsion (VSEPR) Theory. Defined what "electron regions" are and how to count them. The number of regions leads to one of five possible electronic geometries. Each geometry has a name and a specific bond angle(s) associated with it. Then we built new molecular geometries on top of the electronic geometries. They got new names when there were lone pairs as one or more of the electron regions.
10/6MonCovered the concepts and realizations of Valence Bond theory. This is the theory with all the hybrid orbitals in it (sp, sp2, sp3, etc...). Reminder that there are help sheets available on this on this website. I also posted the review sheet for Exam 2 - please download and READ. Hybrids are mathmatical combinations (averages) of atomic wavefunctions (orbitals) that result in the 5 basic electronic geometry shapes that were predicted by VSEPR theory.
10/8WedDiscussed what a (free) radical is (odd electron species) and its properties. Also covered molecular angle "tweaks" where lone pair electrons are more repulsive than bonding electrons. The result of this is an angle in the geometry that is adjusted DOWN by one to three degrees from the original geometry. Also mentioned my dislike of "none of these" as an answer choice on exams. Proclaimed that "none of these" will EVER be the right answer on an exam - something to remember. Showed off the excellent website from Ohio State (see under Links) and looked at VSEPR geometries and then hybrids. Finally, I did introduce the KEY elements of Molecular Orbital (MO) theory. Showed the difference in a bonding orbital and an antibonding orbital.
10/9ThurH08 due at 11:10 PM (night time)
10/10FriMore from Chapter 14 and MO theory. Lilia and Rachel each went through numerous MO examples for 2nd row diatomic molecules. This is definitely something to know for the exam.
10/11SatTX/OU Weekend! TX wins 45-35... you get 2 add-on point to any exam.
10/13MonMore MO theory. Covered heteronuclear diatomic molecules (section 14.4) and delocalization via MO theory - actually a combination of VB theory (LE in your book) and MO theory (section 14.5).
10/14TueH09 due at 11:59 AM (noon!)
10/15WedJudy and Rachel each conducted an exam review.
10/16ThuEXAM 2, 7-9 PM