Today we examine the element fluorine and some ways it affected 20th-century chemistry. The first person to isolate the element was Henri Moissan in 1886, succeeding after many others failed, often with dangerous results. We talk about why fluorine is so reactive. Then we talk of Thomas Midgely's work at General Motors to invent the stable, non-toxic refrigerant Freon. We move to Roy Plunkett at DuPont, who discovered accidentally PTFE, a substance with a remarkably low coefficient of friction, which eventually led to the fabric Gore-Tex, and the fire-extinguishing compounds , the halons. We see how dentist Frederick McKay uncovered the cause of Colorado brown stain, and how fluoride ion protects teeth. We end up with some noble-gas compounds with fluorine, first discovered in 1962.Support the show Support my podcast at https://www.patreon.com/thehistoryofchemistry Tell me how your life relates to chemistry! E-mail me at steve@historyofchem.com Get my book, O Mg! How Chemistry Came to Be, from World Scientific Publishing, https://www.worldscientific.com/worldscibooks/10.1142/12670#t=aboutBook