Put your students in groups of four.
Give each group a bag containing:
--A chocolate chip cookie
--A Tootsie Roll pop (or a Blow Pop)
--A Gobstopper
--A Ferrero Rocher chocolate
The students examine the candies/cookies and discuss which item best illustrates each model of the atom and why.
I like to have students explain why the item is a good model as well as provide a reason why it is not perfect and brainstorm ideas for other objects that would work to represent each atomic model.
Thomson - Chocolate Chip Cookie
Thomson described the atom as having negative charges scattered throughout it, like the cookie has chocolate chips scattered throughout it.
Rutherford - Tootsie Roll Pop
Rutherford first proposed the idea of a nucleus. The Tootsie Roll pop has a dense Tootsie Roll center, or nucleus.
Bohr - Gobstopper
Bohr placed electrons in energy levels, or layers outside the nucleus. Gobstoppers change colors as the oustide dissolves because there are many layers of color.
Heisenberg/Schrodinger - Ferrero Rocher
The Heisenber/Schrodinger model places electrons scattered outside the nuclues - they care in a predictable space but no exact location can be identified. The Rocher candy has a hazelnut center (nucleus). In addition, there are chopped hazelnuts in chocolate surrounding the center - those pieces of nut are found in a specific region, but we can't pinpoint exactly where each piece of nut will be.
In case you aren't familiar with the Ferrero Rocher candies, here's a picture of one, cut through the middle:
At the end of the activity, I allow the groups to divide the items as they see fit. Sometimes serious negotiations take place, but I've never has it turn into an argument (if it looks like it might, all you have to do is threaten to dispose of all the items for them).
A few more ideas/extensions:
--You can add Dalton's orginal atom as a sour ball or other piece of hard candy that's the same throughout.
--You might want to have a knife available, in case a group needs to cut one of the items open. Keep it in your possession and you can do the cutting as directed by the group.
--If you can't bring candy into your classroom, take pictures of the candies and let the students work them out that way. By using materials familiar to the students, they will develop a greater understanding of the models. Going through the Ferrero Rocher model really helped me understand electron clouds better.