Drawing the Electron-Dot Formula for the Ammonium Ion, NH4+
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. Since there are 4 hydrogen atoms, we have 4 electrons.
Nitrogen is in column VA and thus has 5 outer electrons.
We must subtract one electron for the positive charge.
The total number of electrons for all atoms including the loss of an electron for the positive charge is 8.