Question

Due to the small and highly electronegative nature of fluorine, the oxyacids of the this element are much less common and less stable than those of the other halogens. Bonding theory, however, does allow one to propose structures for these acids and use formal charges for the evaluation of these structures. For a molecule of fluorous acid, the atoms are arranged as HOFO. (Note: In this oxyacid, the placement of fluorine is an exception to the rule of putting the more electronegative atom in a terminal position.) What is the formal charge on each of the atoms? Enter the formal charges in the same order as the atoms are listed.

Answer 1

We are told we have an oxyacid of the formula HOFO. We will assume the atoms are in this order and will draw a proper lewis structure for this compound by first drawing bonds between each of the 4 atoms and then place the remaining electron pairs on each atom:
      ..    ..    ..
H - O - F - O:
      ··   ··    ··
We can calculate the formal charge of an atom using the following formula:

Formal charge = [# of valence electrons] - [# of non-bonded electrons + # of bonds]

H: Formal charge = [1]-[0+1] = 0

O: Formal charge = [6]-[4+2] = 0

F: Formal charge = [7]-[4+2] = +1

O: Formal charge = [6]-[6+1] = -1

As we can see the overall charge of the molecule is neutral since the fluorine as a +1 charge and the oxygen a -1 charge.