Isotopes Make Sense When Students Track the Nucleus ... Not Just the NumbersMany students learn isotopes as a vocabulary term: same element, different mass… done.But isotopes are really about how changes inside the nucleus affect the identity and properties of atoms. In this lesson, instead of defining isotopes upfront, students build and analyze atomic models, track changes in neutron count, and observe how those changes impact mass number, stability, and abundance. By examining how atoms of