Question 5. **Periodic trends (15-20)** We have discussed several periodic trends in class, including ionization energy, atomic size, and metallic character. As a class, these six questions were among the most effectively answered on the exam. We also discussed two factors that control all three of these periodic trends in terms of how they are able to control (stabilize) electrons. To answer this exam wrapper question, explain what those two factors that control these periodic trends are; your answer should include a brief discussion of quantum numbers (especially the principal energy level). Also, identify a periodic trend that we have not discussed in class.