10-21-13

This week, we started out with a lecture quiz on sigma and pi bonding, then learned about hybrid orbitals, and had time in class to work on our WebMO.

Sigma bonds are characterized by head to head overlaps and cylindrical symmetry of electron density about the internuclear axis. Pi bonds are characterized by side to side overlaps and electron density above and below the internuclear axis. Single bonds are always sigma bonds because sigma overlaps are greater, which makes a stronger bond and more energy lowering. Double bonds contain one sigma and one pi bond. Triple bonds form with 2 pi bonds and 1 sigma bond. Resonance structures are used to more accurately reflect the structure of the molecule or ion.

We also learned about hybrid orbitals. The electron pairs around the central atom in a molecule are said to be in a set of orbitals (domains) that are hybridized from the usual set of atomic orbitals (s,p,d) for the atom. If one s-orbital and one p-orbital are used-2 hybrid orbitals called sp hybrid orbitals are made. With sp hybrid orbitals there are 2 hybrid orbitals in each set, one s, and one p, 180º between orbitals, and they are linear. With sp2 hybrid orbitals there are 3 hybrid orbitals in each set, one s, and two p, 120º between orbitals and they are trigonal planar. With sp3 hybrid orbitals there are 4 hybrid orbitals in each set one s, and three p, 109.45º and they are tetrahedral. 

We worked a lot on our WebMO diagrams making each of the 13 molecules on the website, finding their angles, dipole moment, and electrostatic potential map. 

My understanding of the two new topics that we learned this week is probably a 9.5. I definitely understand sigma and pi bonds, and I understand hybrid orbitals and could teach them to my classmates if needed. For the test on Tuesday, throughout the week I felt very lost and confused with each of the subjects we had previously learned (such as molecular shapes, bonding, and polarity), but I feel that after doing the WebMO project and the VSEPR Balloon lab report I really understand more of it. The hotpot quizzes really helped, and I took a lot of screenshots of the questions I didn't understand. After studying and working on the projects this weekend I'm beginning to feel a little bit more comfortable about the test on Tuesday. I think that the more I study Monday night, I'll be completely ready for the test on Tuesday....hopefully.