Isotopes, Nuts, Bolts and Eggs

What are we doing to help kids achieve?

 I am always searching for a good isotope activity that I can use with students. I want something that is quick, easy, effective and demonstrates the idea of isotopes and weighted average.  I have tried examples using “pre” and “post” 1982 pennies. The pre 1982 are pennies made of copper. Post 1982 pennies are zinc with copper coating.  There are activities where pre and post pennies can be analogous to an isotope. I have also attempted the same idea with peanut and plain chocolate covered candies that model isotopes. A hazard of that experiment is that the materials are sometimes eaten before the data is recorded.

I have finally found a nice little experiment thanks to the chemistry department at Delta College in Michigan.  Here is how the experiment works. First, I scrounged and found some really cheap plastic Easter eggs.  These represent the “isotopes”. It is helpful to have eggs that are the same color. Next, I went to a tractor and feed store and bought a couple hundred of the cheapest nuts that they had in the hardware section.  About half of these I painted black.  Each group of students then received a bag of about 10 “isotopes” (eggs) and were asked to measure the mass of each (the eggs were numbered for accounting purposes).  Students discovered that about six of the isotopes “eggs” were the same mass, two were lighter and two were heavier. They were asked to put these in groups, to choose one isotope or egg from each group and look inside. Each of the eggs (isotopes) had the same number of black nuts but different number of the silver or non painted nuts.

Now here is where the background information started to kick in. The black nuts were analogous to protons and the silver ones were analogous to neutrons. Students were even able to take the “average” masses a variety of ways and discovered that the weighted average was most similar to their data.

This is the first isotope activity I have tried where the students can look inside the model that resembled the atom and find information that reinforced what an isotope actually is. Furthermore, the quantitative data forced them to examine beliefs about different types of averages and what the numbers really mean. This took a bit to set up but was inexpensive and can be used year to year. Give it a try. Do you have an isotope activity that you like? Why not share in the comments below….

Editor's Note: The activity that this post is referring to has been published as of 10/3/17: An Elemental Understanding of Isotopes.