The charge of a fluorine (F) ion is -1.
Fluorine is a halogen element with atomic number 9, and its neutral state has 9 electrons and 9 protons. When it gains an electron to form an ion, it becomes a negative ion or an anion. Since the number of protons (positive charges) in the nucleus remains the same, and there is an additional electron (negative charge), the overall charge of the ion becomes -1.