From previous experience in teaching the chemistry portion of Science 9, it is apparent that Isotopes remain a difficult concept for many students to grasp. It is very common to see the same mistakes emerge on assignments and tests and remains a persistent issue for many students.
Using the concepts of TGEM (Khan, 2007), I have found generated an activity which works to teach atomic structure and isotopes using the Bill Nye Video and PhET simulation below.
PhET Simulation: Build-an-Atom
Khan, S. (2007). Model-based inquiries in chemistry. Science Education, 91(6), 877-905.