Fluorine F Atomic Number: 9 Atomic Weight: 18.9 ______________________________________________________________________________ Human Physiology: - Strengthens tooth enamel Prevalence: - Found in earth's crust as fluoride compounds (Fluorine is a greenish gas) in concentrations of 540000 ppb(parts per billion) Sources: - Drinking water - Toothpaste Deficiency: - Soft teeth, dental caries Excess: - Nausea & vomiting - Diarrhea - Drooling, numbness, tingling or loss of feeling in extremities - Convulsions - Muscles stiffness - Drowsiness