The hypothetical oxoacid of fluorine, HFO₂(HOFO), would have a positive formal charge on the central F atom.

This is not something that we would expect of fluorine, the most electronegative of all the elements. Hypothetical oxoacids with more O atoms would have the F atom with even higher positive formal charges. Fluorine does form HOF, an oxoacid with no formal charges H—O—F:, but HOF exists only in the solid and liquid states. In water, HOF decomposes to HF, H₂O₂, and O₂.