This worksheet uses candy corn and other candies to explore where atomic mass numbers come from. They weigh various "isotopes" of candy( M&M plain versus peanut) and average their weights based on a percentage represented. Where do the decimals come from in the atomic mass number? The atomic numbers are nice even numbers say 1,2, 27, 71….but the atomic mass numbers are not. This lab is designed to answer that question. The short answer, because the atomic number is the average of all the isotopes of each atom found in the universe. In this worksheet we simulate this averaging with candy.