a. b. 2 c. 3 d. 4 e. S 13. Which of the following is an ionic compound? a. PCIs b. NO2 c. H20 d. KCl e. C2H6 14. Which of the following is/are NOT located in the nucleus of an atom? I. Protons II. Electrons III. Neutrons a. I only b. II only c. I and II only d. I and III only e. I, II, and III 15. How many significant figures should be reported in the answer for the following calculation? 120.2-50.1 a. b. 2 c. 3 d. 4 e.