Fluorine is the lightest member of the halogen family, elements in Group 17 (VIIA) of the periodic table. The halogen family includes chlorine, bromine, iodine, and astatine. Fluorine is the most active chemical element, reacting with virtually every element. It even reacts with the noble gases at high temperatures and pressures. For example, when mixed with water, it reacts explosively. For these reasons, it must be handled with extreme care in the laboratory.
Fluorine was discovered in 1886 by French chemist Henri Moissan (1852-1907). Moissan collected the gas by passing an electric current through one of its compounds, hydrogen fluoride (H 2 F 2 ). The name comes from the mineral fluorspar. Fluorine gas is extremely damaging to the soft tissues of the respiratory tract.
Fluorine is an abundant element in the Earth’s crust, estimated at about 0.06 percent in the earth. That makes it about the 13th most common element in the crust. It is about as abundant as manganese or barium.
CFC and ozone hole are buzz words in the environmental circles. A chlorofluorocarbon (CFC) is an organic compound that contains only carbon, chlorine, and fluorine, produced as a volatile derivative of methane, ethane, and propane. They are also commonly known by the DuPont brand name Freon. The most common representative is dichlorodifluoromethane (R-12 or Freon-12). Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), and solvents. Because CFCs contribute to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs), hydrocarbons,and CO2. However, these replacements are sometimes considered pollutants in their own right.
Fluoride can help prevent cavities, but at high intakes it can harm tooth development (dental fluorosis) and bones (skeletal fluorosis); there is a narrow range between intakes which are beneficial and those which are detrimental. Populations consuming artificially fluoridated drinking water or other fluoridated products, such as fluoridated toothpaste, develop fewer cavities.
References: http://www.chemistryexplained.com/elements/C-K/Fluorine.html#ixzz3WyANyP7Z, Wikipedia