"Fluorine" is also the terminology used for covalently bonded Fl moieties, not just difluorine, the gas. Fluoride is the ion, but if you want to get pedantic,

"Fluorine" is also the terminology used for covalently bonded Fl moieties, not just difluorine, the gas. Fluoride is the ion, but if you want to get pedantic, you're not adding the ion to toothpaste and drinking water - you're adding another fluorine compound which is dissociating in solution. Ie, when you salt your food, you're not tossing in Cl- ions directly.