Chapter 2 - Atoms, Molecules, and Ions - Exercises - Page 76: 2.57e

Charge: -1

Atoms of elements want to have the electron configuration of the nearest noble gas (in terms of number of electrons) on the periodic table. The nearest noble gas to Fluorine (F) is Neon, which is one to the right of Fluorine on the periodic table. Thus, in order to get the configuration of Neon, Fluorine will gain one electron, making the charge of its most stable ion -1.