An ion initially contains 21 electrons. Three outer electrons are removed from the ion. Its relative charge is then measured as +4.
Calculate the number of protons in the ion and its relative charge before the electrons are removed.
Show your working.
103 exam-style questions on Edexcel GCSE Physics 6.1 Atomic structure and isotopes, covering 6.1.1 Structure of the atom, 6.1.2 Isotopes: atomic and mass number, 6.1.3 Sub-atomic particles: masses and charges, and 6.1.4 Electron orbits and energy changes. Each one has a worked solution and a mark scheme showing where the marks go.