: two electrons in a filled inner shell and seven in an outer shell requiring one more to be filled.
It replaced earlier and more toxic compounds, increased demand for kitchen refrigerators, and became profitable; by 1949 Du Pont had bought out Kinetic and marketed several other Freon compounds.
Polytetrafluoroethylene (Teflon) was serendipitously discovered in 1938 by Roy J.
Fluorine is a chemical element with symbol F and atomic number 9.
It is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions.
Reactions of elemental fluorine with metals require varying conditions.
Alkali metals cause explosions and alkaline earth metals display vigorous activity in bulk; to prevent passivation from the formation of metal fluoride layers, most other metals such as aluminium and iron must be powdered, Carbon, as lamp black, reacts at room temperature to yield fluoromethane. Global fluorochemical sales amount to more than US billion a year. Fluorocarbon gases are generally greenhouse gases with global-warming potentials 100 to 20,000 times that of carbon dioxide. Sir Humphry Davy proposed that this then-unknown substance be named fluorine from fluoric acid and the -ine suffix of other halogens. This word, with modifications, is used in most European languages; Greek, Russian, and some others (following Ampère's suggestion) use the name ftor or derivatives, from the Greek φθόριος (phthorios, destructive) . The transition from β- to α-fluorine is more exothermic than the condensation of fluorine, and can be violent.