In January of 2017, Chad Hustings wrote a blog post, Isotopes, Nuts, Bolts and Eggs, about an activity some colleagues and I had shared in a workshop at BCCE in 2016. With encouragement from many ChemEd X readers that wanted to try the activity for themselves, I am sharing more details and a student handout.
About 30-40 minutes for the activity. This depends on how many balances are available to share and how many different isotopes are made for a single element. We had 5 balances for 12 or 13 teams of two students. Students can work in groups of 3 as well.