12 thoughts on “28. Friday, Nov. 13”

1. chem111-mjknapp Post authorNovember 13, 2009 at 4:52 pm

   Kristine,
   the rules are pretty simple, but molecules like O3 are challenging. Some basics to consider:
   1) Fill the octet of the central atom by converting a lone pair from the periphery into a bonding pair.
   2) If there are equivalent atoms on the periphery (eg: two O-atoms), then the bonding will probably also be equivalent – this is why resonance forms are used.
   3) Finally, minimize formal charges as much as possible. This last rule is the key.

   For example, CO2 is best drawn as O=C=O, rather than as one triple bond and one single bond in resonance. This is because the better structure minimzes formal charges, while the worse structure has an excess of formal charges.
2. Prateek Jha November 13, 2009 at 5:00 am

   Hello everyone. I was just wondering if the study group leaders will have the answers to the problems listed at the end of the chapter. I would like to get in touch with one of the study group leaders and possibly discuss the problems after I am through completing them.

   Thank you for your help.
3. Kristine Hughes November 12, 2009 at 10:47 pm

   Also, for anyone whose interested I found a website that does Lewis Structure Tutorials which actually made understanding the basics of setting them up SO much easier.
   http://www.kentchemistry.com/links/bonding/lewisdotstruct.htm
   Just don’t cheat on your OWLs! tsk tsk 😉
4. Kristine Hughes November 12, 2009 at 10:44 pm

   Professor Knapp –
   I’ve been reading and doing the OWLs, and I have this persistent question…when do you know to use a double or triple bond vs. distributing the electrons across the molecule, i.e. in ozone? How do you make the choice to connect one O double and one single? Is there a rule of thumb for this?
5. Danielle Funk November 12, 2009 at 7:33 pm

   Will there be class the day before Thanksgiving? All of my other professors cancelled class.
6. Haley Adelson November 12, 2009 at 1:52 pm

   When will the makeup exam grades be posted?
7. Oksana November 11, 2009 at 8:11 pm

   Thanks Alexander 🙂
8. Alexander Assetta November 11, 2009 at 5:35 pm

   Oksana,
   in that particular question the answer is trigonal pyramidal. if you consult the pop-up table in the question at the bottom of the page it gives you a list of possible molecular geometries for tetrahedral compounds. the previous module explains this concept further.
9. Damian Campanella November 11, 2009 at 4:02 pm

   Here’s a funny comic about octets that I found on the internet
   http://comicjk.com/comic.php/268
10. Michael Donovan November 11, 2009 at 2:24 pm

    ??????
11. Oksana November 11, 2009 at 1:15 pm

    Hello Prof. Knapp, I have a question about hw in owl ( 8.6d VIS – Determining Molecular Shapes: Octet), for the 2nd question it asks for molecular geometry of NF3, I tried everything, including tetrahedral (I think this is the answer). The program would not take it. Please help..

    Thank you.
12. Michael Donovan November 10, 2009 at 12:43 pm

    Prof Knapp. was there any scale or any questions thrown out on the exam? What was the class average? Will these grades stand? Please respond. Thank you.