A great activity to demonstrate how isotopes are atoms of the same element (same atomic number) but different numbers of neutrons (different atomic mass). I use model sets from Frey, but before then I simply used different colored marbles and beads to represent the subatomic particles.
Main topics: atoms, protons, neutron, electrons, atomic mass units (amu), atomic number, isotopes.
If you like this activity, you can follow these links to other lessons and activities in my atoms and elements unit.
Atoms and Isotopes PowerPoint Presentation
Giants of the Atom PowerPoint Presentation
Atomic Models Activity
Atom Review Worksheet
Organizing the Elements PowerPoint Presentation
Properties of Elements PowerPoint Presentation
Adopt an Element Project
Grouping the Elements Worksheet
Classifying Elements Worksheet
Periodic Table Scavenger Hunt
Tour Through the Elements PowerPoint Presentation