Trace levels of this element are detected using particle-induced gamma ray emission or an electrode that uses a “total ionic strength adjustment buffer.” Telomer (“TEE-loh-mer”) alcohols containing this element oligo·merize to form a short-chain propylene oxide dimer acid called GenX. The last digit of a molecule’s R-number indicates its number of atoms of this element, in line with empirical nomenclature. In March 2023, the EPA set a four-parts-per-trillion concentration limit on a carcinogenic octane·sulfonic acid substituted with this element that is still used in firefighting foam. Aluminum smelting is the main source of water pollution by this nonmetal found in cryolite. Because this element forms the strongest single bond with carbon, inert alkyl surfactants containing it are colloquially called “forever chemicals.” For 10 points, name this element found with carbon and chlorine in freons and other ozone-destroying molecules. ■END■
ANSWER: fluorine [or F; reject “fluoride”] (“Forever chemicals” include PFAS, or perflouroalkyl and polyfluoroalkyl substances. The ozone-destroying molecules are CFCs, or chlorofluorocarbons.)
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