10/7-10/11

            This week in AP Chem we worked a lot more on Lewis structures. We specifically clued in on expanded octets in Lewis structures and also which Lewis structures is more correct. We spent some time with pogils and also did some practice problems to further our knowledge.

            Up to this point, we knew that there was a certain checklist needed for making Lewis structures. First, one must determine, from the compound, which atom is the least electronegative and place this atom as the center atom. You choose the least electronegative atom as your center atom because you want this atom to be the least likely to take away electrons from atoms and be the most likely to share electrons with other atoms. Next, you must create bonds with the pairs from the outside electrons and the inside atom and complete the octets for each atom. (Note: Hydrogen has a complete octet with two electrons.) We then want to place any remaining unpaired electrons around the inside atom.

            This week we spent time going over what we learned on formal charges in a lecture last week. Formal charges can be defined as the number of valence electrons an atom as minus the bonds it has attached to it minus the number of unbonded electron pairs surrounding the atom. With the pogil we did we were able to determine that the most correct Lewis structure is the one that has the least formal charges, preferably a overall formal charge of zero on the compound. We learned that for certain atoms like oxygen you can have the formal charges memorized. If there is only bond attached to oxygen, it has a formal charge of -1. If there are two bonds attached to oxygen there is a formal charge of 0. If there are three bonds attached to oxygen, there is a formal charge of +1. There are many other atoms like oxygen which we need to have their formal charges based on number of bonds attached to them memorized. By doing our pogil on formal charges, we also learned that you can take unbonded electrons on the outside atom and move them down to create a bond between the inside and outside atom to change the formal charge.

            We also did another pogil on expanded octets. We learned that elements in the third period or lower can have extra pairs of electrons placed around them that can be more than a complete octet. This is because elements in the third period or lower have access to the d-orbital.

            I don’t really have any questions on what we did this week. It all connects together in my head and I have a good grasp on drawing Lewis structures. My participation was there in everything that we did this week and therefore I have a better grasp on Lewis structures than I did before. I still need to practice drawing Lewis structures to get better and better.