Week 6 Blog Entry

This week in AP Chem, we began compiling a table of the thirteen different molecules we used back in our first VSEPR POGIL. We used software called WebMO. This is a neat computer program that lets you create any molecule and then submit it as a job, where it can then be optimized for different forms. For example, we used the geometry and molecular orbital optimization. From this software we could record the bond angles of the molecule, find and display the dipole moment, and also create electrostatic potential models that showed the polarity of the molecule. We then took all of this information and compiled it in a table, which we then used to create a full lab report on each of the 13 molecules.

I was kind of confused at first when making the molecules; I had to scrutinize the instructional packet in order to reassure myself that I was performing the steps correctly. However, after two or three molecules, I had gotten the hang of creating new molecules and soon enough, I whipped out nearly ten molecules by myself (molecular and geometry optimization) within the first period! It became quite methodical for me, and I was really impressed by the growing ease with which I could identify the molecular shapes. I remember looking at the molecular optimization of BF₃ and unconsciously identifying it as a trigonal planar molecule. I was quite surprised how fast I arrived to that conclusion, when just a week earlier I was struggling with the VSEPR balloon molecules and scratching my head over how to determine the shape and bond angles. The WebMO models really helped me gain a lot of practice on determine VSEPR shape.

On day two of model making, we optimized the electrostatic potential models for each molecule. This was incredibly helpful for clarifying the concept of polarity for me. When completing the polarity lecture quiz, I really couldn’t wrap my head around the concept of how electrons would be more dense in certain parts of the molecule. The electrostatic maps showed the electron density through the use of color, where the more red areas would represent more electrons and the blue areas would signify fewer electrons. In every case, the more electronegative atoms in the molecule were surrounded by red. This is because these atoms attract more electrons, resulting in a more electron-dense area.

I could also see why some molecules were overall nonpolar even if they had polar bonds. I could visualize the surrounding atoms as horses pulling outwards from the central atom. If they were symmetrically spaced from each other about the central atom and pulled with the same strength (magnitude), then they would all cancel out and result in a net dipole moment of 0.

At the end of the week, we did some reviewing of our upcoming test. We discussed polarity and whiteboarded some questions from Lectures 9 & 10. As usual, the whiteboarding really helped me gain some extra tips on how to go about solving a chemistry problem. Each of my classmates has a different way of approaching a problem, and that became visible when each group demonstrated their answer for the whiteboard questions. Whenever a group did not correctly answer a question, it was very helpful when Dr. Finnan went through the reason why it was incorrect because I would often make the same mistake the group did.

Overall, I feel much more confident in my knowledge of Lewis structures and VSEPR models. I have become stronger in polarity, but I still have some reviewing to do to feel completely sure of myself. I also have some touching up to do on concepts like sigma and pi bonding, and bond orders/lengths.