Drawing the Electron-Dot Formula for Water, H2O
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 2 hydrogen atoms, the total for hydrogen will be 2 electrons.
Oxygen is in column VIA and thus has 6 outer electrons...again remember that we don't use the atomic number for electron-dot formulas.
The total number of electrons for all atoms is 8. What do you do next?