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'''Fluorine''' is the lightest member of the [[halogen]] elements, or Group VIIa of the periodic table. It is also the most reactive chemical element. Fluorine is so dangerous that it must be stored in steel containers, and even then it reacts with the steel. Fortunately, the layer of fluoride that is formed is unreactive, and prevents it from reacting further. Fluorine is a component of many drugs, and its [[radioisotope]] is used in functional brain imaging and bone scans. Under ordinary conditions, pure fluorine is a [[gas]] with a pale yellow color. <ref>[http://www.britannica.com/eb/article-9034677 ''Fluorine'']</ref>

== Uses ==