With fluorine, the roles of atoms in oxygen compounds are reversed. All of the atoms through nitrogen were less electronegative than oxygen, with the result that electron pairs were shifted toward O or donated to O outright.

In contrast, fluorine is more electronegative and pulls electrons toward itself, even in bonds with oxygen. Fluorine has several oxygen compounds, which are chain molecules of the type F-O-F, F-O-O-F, F-O-O-O-F, and so on. These are rare and unimportant, and do not produce oxyacids, such as boric, carbonic, and nitric acids, when added to water.

Fluorine is so electronegative that it does not make covalent bonds with coordinating oxygen atoms in water, but steals electrons from them instead to make fluoride ions. breaks up water molecules and releases in the process of producing fluoride ions:

In writing formulas of binary compounds, the more electronegative element is written second. Thus writing instead of and naming the compound oxygen difluoride, rather than difluorine oxide, is a reminder that in this compound fluorine is the more electronegative of the two elements.