Unit:

Students use the APH atom model to both become familiar with the concept of atomic number and mass number and to display (model) their understanding of these concepts. These concepts are much clearer and more concrete for students who are blind or visually impaired when taught with a model. I find the APH model to be an excellent resource. The atom model is part of the Azer Periodic Table Set (link) and can also be purchased separately

See the following link for a review of the entire set: http://www.perkinselearning.org/accessible-science/azers-interactive-periodic-table-study-set and the following link for a review of the atom model only: