An atom of chlorine-35 and an atom of chlorine-37 are isotopes. Which statement explains why they are isotopes of the same element?
They have the same mass number but different numbers of protons.
They have the same number of protons but different mass numbers.
They have the same number of neutrons but different mass numbers.
They have different numbers of protons and different mass numbers.
40 exam-style questions 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). Each one has a worked solution and a mark scheme showing where the marks go.