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.
What do you do next?