Worksheets on AQA GCSE Physics 4.1 Atoms and isotopes, covering 4.1.1 The structure of an atom, 4.1.2 Mass number, atomic number and isotopes, and 4.1.3 The development of the model of the atom (common content with chemistry), with answers. Print them, or work through one on screen. Write your working straight onto the paper and Genie marks it question by question against the mark scheme.