After voting, two or three students can be selected to calculate the structure on the chalkboard, while the rest of the students do so with paper and pencil. They walk through the formal calculations and compare their answers to the results of the voting at the beginning of the class.
This activity reinforces formal charge calculations, and gets the students talking to each other. Part of the goal is to understand that science is a process in which sometimes the answers are unpredictable, but using the skills from the class, they can figure out something that makes sense.
For Katherine Phillips, one of her sections reacted more favorably to the activity than the other section. Use this activity if you think the students will enjoy the competition.