Computer simulations help students visualize isotopes in an accessible way (an extension of the lesson "Inquiry Based Learning for Computational Simulation of the Atom"). Through constant feedback, stuents are encouraged to ask and test their own questions during the inquiry process.
 
In this lesson, students are introduced to the concept of the isotope through the real-world example of radioactive isotopes in medicine. They further explore isotopes with the Phet Simulation, building different isotopes and look for patterns in subatomic particles. Students then explore visually and with simulation how different combinations of isotopes lead to different average atomic masses.  These quantities are typically abstract for students, but the simulation makes them more accessible.