Igloo writes Fluorine is one of the elements with only one isotope, and this has: 9 protons, 10 neutrons and 9 electrons. So the total number of particles is 28. You work this out from the atomic number (proton number) and the mass number (total number of neutrons and protons) remembering that in an atom the number of electrons equals the number of protons. Risk assessment Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website. For further guidance see our tutorial on Risk Assessment.