Elemental fluorine has been studied as a rocket propellant as it has an exceptionally high specific impulse value. Compounds of fluorine with rare gases have now been confirmed. Fluorides of xenon, radon, and krypton are among those known. Elemental fluorine and the fluoride ion are highly toxic. The free element has a characteristic pungent odor, detectable in concentrations as low as 20 ppb, which is below the safe working level.
Fluorine is known to have thirteen isotopes.
15.69 eV Forms fluorides with all elements except helium, neon, and argon. Gaseous fluorine and ammonia emissions from two pulverized coal power plants were measured over a 6 month period. The difference in fluorine between units was related circumstantially to ash content. Neither gas was in sufficient quantity relative to sulfur dioxide to influence net acidity. Levels of fluorine were comparable to those of other combustion sources and the aluminum industry.