HollyAsChemBlog: Chemical Bonding

Molecular Shapes Practice

Since I have been struggling understanding molecular shapes and how to apply this concept, I decided to look up some videos and practices to do before our final test, this way I should be more comfortable. http://www.softschools.com/quizzes/chemistry/lewis_structures_molecular_shapes/quiz939.html
http://people.cornellcollege.edu/cstrong/courses/vsepr_practice1.htm
http://butane.chem.uiuc.edu/anicely/chem102Dfa10/Worksheets/Worksheet13_VSEPR_Key.pdf

http://ths.talawanda.org/~bramblen/classroom/Pictures/molecularshapenotes.JPG

YouTube Video Help:
https://www.youtube.com/watch?v=keHS-CASZfc

In class for our second lesson, we talked about the various shapes a molecule can take as well as resonance To have resonance, it means that a compound had multiple bonds, and when you move one of the bonds it has, it must fit in any given place. This is what it looks like:

https://upload.wikimedia.org/wikipedia/commons/thumb/e/ed/Carbonate-ion-resonance-2D.png/380px-Carbonate-ion-resonance-2D.png

As shown, the double bond can be moved to any of the three sides of the molecule, and it is still the same; This means it has resonance.
The next thing that we talked about are the selection of shapes that the molecules that we deal with can have. The five primary shapes that our teacher told us we would be working with are: a trigonal planar molecule has three bonded entities to the central atom and the central atom does not have any lone pairs, a tetrahedral molecule which has 4 bonded entities around one central atom, a linear molecule has two bonded entities to the central atom and this does not have a lone pair, a trigonal pyramidal molecule which has three bonded entities and one lone pair of electrons around the central atom, and a bent molecule which has two bonded entities with two lone pairs of electrons around the central atom.
This is what these five look like:

http://cnx.org/contents/d5d1d182-3eb0-419a-bfda-3615e56fafea@1

Here are some more links to help. I found the shapes to be fairly tricky to remember and practice.
http://intro.chem.okstate.edu/1314f00/lecture/chapter10/vsepr.html
https://www.chem.wisc.edu/areas/clc/organic/343/02_resonance_structures_343_ans.pdf

First Unit Lesson

Our first lesson for out new unit over chemical bonding was reviewing the Lewis Dot structure that some of us learned back in Freshman year. This model is when you take the element symbol and place the electrons around the outside on each of the four sides clockwise and singularly, then you can double.

http://www.middleschoolchemistry.com/img/content/multimedia/chapter_4/lesson_6/lewis_dot_table_big.jpg

We also learned about the octet rule, which states most elements can only hold eight electrons in their valence shell, but we also leaned there are exceptions to this. These are that Hydrogen and Helium only have up to two, Boron requires six, and Beryllium only needs 4.

To end the lesson, we went over the Have, Need, Share chart to determine the number of electrons and bonds to place on the diagrams.

Here is what that type of diagram looks like: