Use gumdrops and toothpicks to build a model of CaCO3. b) Select one color of gumdrop for calcium, a second color for carbon, and a third color for oxygen. Be sure to include a key of your chosen color scheme with your model. c) Use the periodic table to help you determine the number of bonds each atom will form. Step 4: Build models of the products. a) Use gumdrops and toothpicks to build a model of CaO and a model of CO2. b) Be sure to use the same colors of gumdrops for calcium, carbon, and oxygen as you did in Step 3. Include a key of your chosen color scheme with your models. c) Use the periodic table to help you determine the number