What is the typical oxidation number of fluorine in compounds?

• A. 0
• B. +1
• C. +2
• D. -1

Answer: (D)

Fluorine is the most electronegative element, so in almost all compounds it attracts the bonding electrons toward itself. Using the usual rule for oxidation numbers—that electrons in bonds are assigned to the more electronegative atom—fluorine ends up with an oxidation state of -1 in compounds. The only time its oxidation number is not -1 is when fluorine exists as the element F2, where there are no bonds to other elements and the oxidation state is 0. Since there’s no situation where fluorine becomes positive in typical compounds, -1 is the standard oxidation number for fluorine in compounds.