(2) Refers to a molecule
in which all hydrogens bonded
to carbon have been replaced by an atom of the same element such
as fluorine or chlorine.
Shown here is perfluorooctanoic
acid (PFOA), formerly used as a surfactant
in numerous products. The use of this molecule
is now under scrutiny because it is a toxicant and carcinogen
in animals, and persists indefinitely in the environment, showing
little or no biodegradation
over time.
