1 electron. Look at the periodic table, fluorine (F) is on the right, atomic number 9. It wants to get all the way over to the right to become more stable, which means it only needs 1 more electron (has 7 in its current state, wants 8)
Not quite, fluorine is valency one which indicates that fluorine would only needs ONE electron to obtain the octet (being that it already has 7 electrons on its valence orbital) and as such it gains one electron to form the fluoride ion ( Fl⁻).
