During a previous post, I talked about ionic, covalent and metallic bonding -- today, I'm going to revisit some other topics related to Bonding.
Objectives:
1. Draw Lewis structures to show the arrangement of valence electrons among atoms in molecules and polyatomic ions; explain the difference between single, double, and triple covalent bonds.
2. Predict the shape of a molecule using VSEPR theory.
Lewis dot and line structures are part of the language of chemistry and are important for students to be able to be fluent in the language of chemistry.
Here is one teaching video to introduce the subject. It's 20 minutes, but it's a good overview -- and, dude, this narrator is enthusiastic!
Objectives:
1. Draw Lewis structures to show the arrangement of valence electrons among atoms in molecules and polyatomic ions; explain the difference between single, double, and triple covalent bonds.
2. Predict the shape of a molecule using VSEPR theory.
Lewis dot and line structures are part of the language of chemistry and are important for students to be able to be fluent in the language of chemistry.
Here is one teaching video to introduce the subject. It's 20 minutes, but it's a good overview -- and, dude, this narrator is enthusiastic!
I teach my students to count how many electrons it would be if full octets are entered (and duets if hydrogen is involved) -- then to check if it matches the total number of valence electrons calculated. This helps students to determine if they are dealing with exceptions to the octet rule.
Here is a very simple worksheet. It could be used to teach Lewis structures -- you could project the image on an overhead projector to teach the structures. You may want to switch back and forth from notes to this page during your lesson.
Here is a very simple worksheet. It could be used to teach Lewis structures -- you could project the image on an overhead projector to teach the structures. You may want to switch back and forth from notes to this page during your lesson.
Here is another link to blank worksheets and a corresponding answer key:
http://teacherweb.com/WA/CloverParkHighSchool/Meldrum/Electron-Lewis-Dot-IampII-and-answers.pdf
One pair of electrons being shared is called a single bond and is drawn with a single line -- for example, H-H. Two pairs (or four) electrons being shared is called a double bond and is drawn with two parallel lines. An example is O2. Three pairs (or six) electrons being shared is called a triple bond and is drawn with three parallel lines. An example is N2.
Here is another video talking about Lewis structures and VSEPR theory. The acronym VSEPR stands for Valence Shell Electron Pair Repulsion and helps to determine the 3-dimensional structure of a molecule whereas the Lewis structure is 2-dimensional.
The theory is that the molecule's shape will decrease the interactions of the valence electrons. Because they are negatively charged they repel, and the molecule shape is to maintain the bonds but keep those electrons as far away from each other as possible.
Whatever shape the molecule takes, it is considered to be stable in this configuration because it minimizes the interactions of the valence electrons. I'll talk about that more when I cover energy and potential energy diagrams in another post.
Here is a video talking about VSEPR theory -- it's longer (about 20 minutes):
http://teacherweb.com/WA/CloverParkHighSchool/Meldrum/Electron-Lewis-Dot-IampII-and-answers.pdf
One pair of electrons being shared is called a single bond and is drawn with a single line -- for example, H-H. Two pairs (or four) electrons being shared is called a double bond and is drawn with two parallel lines. An example is O2. Three pairs (or six) electrons being shared is called a triple bond and is drawn with three parallel lines. An example is N2.
Here is another video talking about Lewis structures and VSEPR theory. The acronym VSEPR stands for Valence Shell Electron Pair Repulsion and helps to determine the 3-dimensional structure of a molecule whereas the Lewis structure is 2-dimensional.
The theory is that the molecule's shape will decrease the interactions of the valence electrons. Because they are negatively charged they repel, and the molecule shape is to maintain the bonds but keep those electrons as far away from each other as possible.
Whatever shape the molecule takes, it is considered to be stable in this configuration because it minimizes the interactions of the valence electrons. I'll talk about that more when I cover energy and potential energy diagrams in another post.
Here is a video talking about VSEPR theory -- it's longer (about 20 minutes):
The lab possibilities are mainly building models of various molecules. Check to see if your department has molecular model kits. To ensure that the kits are returned without pieces missing, you might want to have students sign them out and back in so they take responsibility for the completeness of the kit.
I purchased a set of Styrofoam spheres at a local craft shop (sewing stores might have them as well) for demonstration with toothpicks. I was able to purchase the Styrofoam balls in both larger and smaller sizes, so I was able to use the larger sphere as a central atom and the smaller Styrofoam balls as the attachments.
Here is a quick (short) lab handout:
http://www2.volstate.edu/chem/1110/Molecular_Modeling.htm
This lab is a little longer, but the chart is handy:
http://www.celinaschools.org/Downloads/MOLECMOD_Lab.pdf
*I'd love to hear from you! Your feedback would really help me to focus on your needs, so write to me! Simply click on the "Contact" tab.
I have started a Twitter account and hope this post (or a link to it) will show up!
For other lab ideas, check out my lab book "Chemistry on a Budget" at amazon.com:
http://www.amazon.com/Chemistry-Budget-Marjorie-R-Heesemann/dp/0578129159/ref=sr_1_1?s=books&ie=UTF8&qid=1389410170&sr=1-1&keywords=chemistry+on+a+budget
Each lab is presented with two possible report formats -- both with the same procedure -- one with 10 questions to be answered as a conclusion, the other with a full laboratory report required. This was to give the teacher the option of what type of report is desired!
Have a good week!
I purchased a set of Styrofoam spheres at a local craft shop (sewing stores might have them as well) for demonstration with toothpicks. I was able to purchase the Styrofoam balls in both larger and smaller sizes, so I was able to use the larger sphere as a central atom and the smaller Styrofoam balls as the attachments.
Here is a quick (short) lab handout:
http://www2.volstate.edu/chem/1110/Molecular_Modeling.htm
This lab is a little longer, but the chart is handy:
http://www.celinaschools.org/Downloads/MOLECMOD_Lab.pdf
*I'd love to hear from you! Your feedback would really help me to focus on your needs, so write to me! Simply click on the "Contact" tab.
I have started a Twitter account and hope this post (or a link to it) will show up!
For other lab ideas, check out my lab book "Chemistry on a Budget" at amazon.com:
http://www.amazon.com/Chemistry-Budget-Marjorie-R-Heesemann/dp/0578129159/ref=sr_1_1?s=books&ie=UTF8&qid=1389410170&sr=1-1&keywords=chemistry+on+a+budget
Each lab is presented with two possible report formats -- both with the same procedure -- one with 10 questions to be answered as a conclusion, the other with a full laboratory report required. This was to give the teacher the option of what type of report is desired!
Have a good week!
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