Drawing the Electron-Dot Formula for the Hydroxide Ion, HO-
The first thing that you must do is to determine the number of electrons available for the formula?
Hydrogen is in column IA and thus has 1 electron.
Oxygen is in column VIA and thus has 6 outer electrons.
We must add one electron for the negative charge.
The total number of electrons for both atoms including the extra electron for the negative charge is 8.