1/30/14 Molecular Geometry

Mrs. Friedmann started off class by telling us what our homework is for tonight. We have 2 web assigns due at 11:59, another VSEPR handout to do, and we should check moodle for the key to the worksheets we did yesterday. Plus, we have another quiz tomorrow which will be on all the stuff we've been learning about molecular geometry.

In class, Mrs. Friedmann had us finish the VSEPR chart that we started yesterday. This is similar to what we ended up with:




 We are supposed to have this memorized for tomorrow, and Mrs. Friedmann suggested 2 ways. We can either memorize the VSEPR code (ABE) and memorize all the corresponding shapes. . .
OR we can try to visualize what shape the molecule should be just by using our knowledge of the number of clouds and how that number will impact the formation of the molecule. Mrs. Friedmann suggested the latter.

After we finished up the chart, Mrs. Friedmann introduced something called Wedge and Dash Drawings to us, which is a technique for drawing 3-D molecules more clearly. The way it works is that you either use a normal line like this ___ to represent 2-D bonds, a wedge to represent the bonds that stick out towards you, and a dashed line like this - - - to represent the bonds that stick away from you. It's difficult to explain with words, so here's an example:
  It's just an optional, easier way to draw 3-D shapes.

And that's all, so. . . good luck on the quiz everybody!


The next blogger is Brandon Moy

Molecular Geometry

By: Katie Coy

Reminders:

We started off class today with a few reminders:

1. Make sure if you have not taken the quiz that we took in class on Friday that you do so ASAP
2. If you were absent on Friday and today, make sure to show Ms. Friedmann your notes that you took on the two videos (Thursday nights homework.)

Molecular Geometry:

Today we began a new concept called Molecular Geometry. Below are the notes that I took, but you can always go get a copy of Ms. Friedmann's notes off the Unit 7 Notes box on Moodle. Without further ado, here are the notes that we took in class today:

Molecular Geometry (essentially creating a 3D model of a Lewis Structure for a molecule)

 

     A. Molecular geometry is a 3D picture that is representing a more accurate model of how the electrons are spaced around a central atom (the atom in the middle of a Lewis structure.) Lewis Structures show only a 2D model of electrons, whereas Molecular geometry attempts to show a more accurate model of how electrons in the electron cloud (explained in part C) are actually formatted. 

    B. VSEPR- stands for Valence Shell Electron Pair Repulsion

          1. 'clouds' of electrons surrounding a central atom are attracted to the central atom, but since electrons all have a negative charge, they repel each other. Therefore, the most stable state for an electron is to position itself as far away from other atoms as possible. 

     C. There are two kind of electron clouds or things that the electrons live in around the central atom

          1. a pair of electrons in a cloud (bond)

          2. a pair of unbonded electrons (aka a lone pair)

     D. In deciding molecular geometry ask yourself two questions:

          1. how many clouds (either bonded or unbonded) are around that central atom?

          2. how many clouds are bonding and how many clouds are unbonded (or just have a pair of electrons in it?)

The Different Geometries- aka how to actually draw the 3D shapes of molecules

    A. Code: this code is used by chemists to represent all the stuff (atoms, bonded electrons, and unbonded                       electrons) in a molecule. The code is as follows:

          1. A= central atom

          2. X= terminal atoms (atoms that are attached to the central atoms by bonds)

          3. E= electrons that are on the central atom itself (aka lone pair electrons)

   B. Vesper Code                           # of Clouds                            Geometry name

       AX2                                             2 clouds                          Linear (180 degrees)

       AX3                                             3 clouds             Trigonal Planar (120 degrees)

       AX2E                                           3 clouds                     Bent (about 120 degrees)

       AX4                                             4 clouds                 Tetrahedron (109.5 degrees)

       AX3E                                           4 clouds    Trigonal pyramid (about 105 degrees)

       AX2E2                                         4 clouds                      Bent (about 105 degrees)

    C. The VESPER code as seen above is not complete because the # of clouds can go up to 6. In order to fill out the two worksheets homework for tonight, you need to know up to the 6th cloud. This information can be found on this website: http://www.sfponline.org/Uploads/15/VSEPR%20handout.pdf. Also, do not worry if you do not understand completely what this means at all. For the people who were absent today, we just began to familiarize ourselves with this EXTREMELY new concept and confusion is expected. My best explanation for how to use the VESPER code (as seen above) is through an example:

     D. For example,  lets say we have CO2 and the Lewis structure looks like this:

Lewis Structure of CO2

        As one can see there are two electron clouds, because there is the left double bond with carbon and the right double bond with carbon. Anyways, to figure out the correct molecular shape of CO2, consult the table seen above. Which VESPER code shows the formula for having one central atom (carbon) and two terminal atoms (the left and right oxygen?) That's right... AX2 seems to be the right VESPER code so that means that the geometry name for CO2 is linear with a bond angle (the angle between bonds) of 180 degrees. In turn this results into the shape of CO2 on a 3D model being as follows... 

Focus on the right diagram for this is the molecular geometry of CO2

I hope that my example was helpful. If you need more explanation or help, Ms. Friedmann posted a link to a site in the Unit 7 Moodle box that has a Java program that will help you visualize molecular geometry much better! (Just a side note, this program will need Java to run so it will not run on the Chromebooks!)

Homework:

1. Two Webassigns are due by 11:59 pm tomorrow night
2. Try the two handouts 'Molecular Shapes form Lewis structures" due tomorrow
1. Just a note that this can be found in the Unit 7 handouts folder and again this concept is new and confusion is expected.
3. Have a wonderful night :)

I almost forgot.. the next blogger is Lauren Benson  

 

What is a Bond?

Katie Coy 

Today we started off class by meeting our substitute, Mrs. Yudell, who was filling in for Ms. Friedmann. After we greeted Mrs. Yudell, we went over the answers to the two worksheets that were assigned for Thursday nights homework (What is a bond? How and Why Does it Form?) If you were absent, the answers to these two worksheets can be found in the Unit 7 Keys folder. Even though the keys have not been posted yet, I am sure we will go over them in class due to Ms. Friedmann's absence. (Do not worry if you do not completely understand the worksheets:).) After checking those two worksheets, Mrs. Yudell handed out the quizzes. If you were absent today, make sure to talk with Ms. Friedmann so you can take the quiz.

Homework:

• The Molecular Geometry Packet (I'm assuming this packet will be put into the Unit 7 handouts folder by the end of the weekend. Also, the information in the packet is fairly new, so it is completely normal to feel lost.)
• Finish the notes on the two videos that were assigned Thursday, Ms. Friedmann will check them in on Monday.
• Have a great weekend!!!

Lewis Structures

The next blogger is.... me!

Covalent Bonds and Lewis Structures

To start off...
Yesterday, the class did not have enough time to completely go over covalent bonding, so we finished the notes today (posted in the unit 7 notes folder). In addition we redid yesterdays homework about Lewis Structures in class, to serve as a good review about Lewis Structures. Finally Mrs. Friedmann began the worksheets "What is a Bond?" which we are suppose to complete for homework.

Notes Review...
- Here is a good review about Lewis Structures from one of the Crash Courses Videos...

Here are the exceptions to the octet rule discussed today...

- Hydrogen needs 2 electrons not 8

- Boron needs 6 electrons not 8

- Everything including the third period and down the periodic table can hold more than 8 electrons if it has to.

Homework..

1) Finish the "What is a Bond?" pair of worksheets we began in class today.  Due tomorrow.

2) WebAssign 7.1a-Covalent Bonding and LED -- due tonight by 11:59 pm.

3) Watch the two videos posted in the Unit 7 box:  "Covalent Bonding" and "Bonding Models and Lewis Structures".  Take notes on both videos in your journals, to be checked in tomorrow.

4) Quiz tomorrow on bonding and Lewis Structures!

Examples of Lewis Structures

The next scribe is Katlin Coy

Summary January 22

Today in class, we checked in our homework and picked up 3 worksheets (You can most likely find these online.)  We also received a yellow slip that was to decide what class (physics or honors physics) that you want to take next year.  There are also other electives that you might be interested in taking instead.  These include forensics, horticulture, astronomy, brain studies, AP chem, AP bio, AP physics, honors engineering physics, or med tech.

Next, we went over last night's homework.

Just to review, Ionic compounds are formed when atoms transfer electrons to each other (metals lose electrons, nonmetals gain them) in order to achieve a stable valence (usually 8, a perfect octet).  As a result, the atoms become ions.  The attraction between positive ions and negative ones forms the ionic bond.

Then, we started to talk about covalent bonding in class today.  The notes will be posted in the Unit 7 notes folder.

The homework for tonight was the 'Practice Building Lewis Structures' worksheet that we picked up.  Also, we have our first webassign of second semester!! This will be due tomorrow night and you have two attempts to get the best score you can!

The next blogger will be......... Ambreen A!!

Summary for January 21st

The first day of the new semester!

By: Jordan C.

Mrs. Friedmann started off the class with her unique life-view on choosing next year's classes. She made it evident that the class levels should depend life's balance rather than doing everything possible. However, it is ultimately up to the student. She made a point to say her experience in college was overwhelming in the sense that she took 18 credits the first year on top of other rigorous activities. This led to fatigue by the end of the year. It is important to take into account the balance in classes for the upcoming junior year.

We then led off to the next part of class with some review notes on ionic bonding. The majority, if not all, was review from the first semester. This can be viewed on the Moodle page or using this link below. Her commentary went along with the notes quite nicely.

Notes

The next part of the class was time set aside to start on the homework. The homework is the following:

1) Complete the Intro to Ionic Bonding worksheet -- due tomorrow.
2) Complete the ChemThink tutorial and question set for Ionic Bonding. You have already done this ChemThink, so the program might not recognize that you've completed it for a second time. Don't worry, just complete it to refresh your memory on the fundamentals of ionic bonding.

As a side conversation, the decision has not yet been made on whether we will study nuclear or organic chemistry. 

Elayna M. will be the next blogger! :D