Isotopes of chlorine Isotopes of chlorine Chlorine (Cl) has 25 isotopes with mass numbers ranging from Cl to Cl and 2 isomers (Cl and Cl). There are two principal stable isotopes, Cl (75.78%) and Cl (24.22%), giving chlorine a standard atomic weight of 35.45. The longest-lived radioactive isotope is Cl, which has a half-life of 301,000 years. All other isotopes have half-lives under 1 hour, many less than one second. The shortest-lived are Cl and Cl, with half-lives less than 20 and 30 nanoseconds, respectively—the half-life of Cl is unknown. Bromine is the only other halogen with more than one stable isotope. Trace
Biological aspects of fluorine Biological aspects of fluorine Biological aspects of fluorine describes the effects of fluorine-containing compounds with life. Fluorine (F) itself is very rare in everyday life, but hundreds of fluorine-containing compounds occur as minerals, medicines, pesticides, and materials. Naturally occurring organofluorine compounds are extremely rare. Nonetheless, twenty percent of all commercialized pharmaceuticals contain fluorine, examples being Lipitor and Prozac. Manmade fluorinated compounds have also played a role in several noteworthy environmental concerns. Chlorofluorocarbons, once major components of numerous commercial aerosol products, have proven damaging to Earth's ozone layer and resulted in the wide-reaching Montreal Protocol (though in truth the chlorine in