Resonance Structures, Formal Charge, VSEPR

This week we continued to study VSEPR, resonance structures, and formal charge.

First we finished up our VSEPR balloon and gumdrop lab. Each group presented about the different molecules that they modeled and we filled out the chart in the VSEPR Theory Lab packet. Since the gumdrop models represent the molecular domain geometry, some of the molecules had structures that differed from the balloon electron domain models. This is because when creating the molecular domain structures non-bonding pairs of electrons are not included in the model. We also learned that these non-bonding electrons can cause the angle between the central atom and the other atoms to be less than the angle expected, because they push down on the bonds. Another thing that we learned about through this investigation was how to write molecular class.

Writing Molecular class:
-Write A as the central atom 
-Write B to represent bonded atoms, use subscripts if more than 1.
-Write E for lone pair electrons, use subscripts if more than 1.

 

Next we talked about Lewis structures and formal charge. We did POGIL 16 to learn more about creating Lewis structures and how to decided which structure is more correct. We learned that the element with the lowest formal charge is the structure that is more correct. To figure out the formal charge you subtract the number of lone pair electrons and the number of bonds from the number of valence electrons of the element. You write a + or - inside of a circle for +1 or -1 and for other numbers you write them inside the circle too. If there is 0 charge then nothing is written. 

FC= (# of valence electrons that the element has) - (number of non-bonding electrons)- (number of bonds)

We learned that in some cases atoms could have a charge that canceled with another atom's charge to create a neutral molecule with a formal charge of 0. In order to determine if the structure is the best structure you must make sure to find the charges of all of the atoms. This technique can be used to determine what resonance structure is more likely to occur in nature. 


 Another thing that we discussed this week was expanded octets and how to draw Lewis structures that have a formal charge of 0.We did POGIL 17 to learn more about hypervalency and formal charge. We learned that in order to have a formal charge of 0, double or triple bonds may have to be formed. We also learned how to find the bond order in more complex molecules. 

 

 At the end of the week, we did a white boarding activity that tied all of the ideas of the week together. In this activity we worked with our table groups to determine the Lewis structure,  molecular class, electron domain geometry, molecular domain geometry, and the angles of the bonds for different molecules. We did this for I3-,  BSF, NSF, SCN-, SO2, and GeS2.

Over all this week I think my understanding of the material improved each day. I felt that the white board activity on Friday helped me to put all of the information together and know how it all relates . I enjoyed working with my group and I think that we all gained a better understanding of the material through out that class period. For me personally I would give my understanding of the material a 8.5/10. This is because I feel that I have a good understanding of the material, but I feel that I need to do more practice since I just recently figured out how it all is related.