Chemistry 115

General Rules for Writing Lewis Dot Structures

1. Arrange the atoms so that the ones that are bonded together are next to each other.

a) if a formula has only one atom of a certain kind, that is usually the central atom.

b) given a choice, oxygen tends not to be the central atom.

c) halogens are rarely the central atom.

d) hydrogen and fluorine are never the central atom.

2. Find the total number of valence electrons.

a) add up the number of valence electrons for each atom in the molecule.

b) add or subtract electrons is there is a charge on the molecule.

3. Start distributing the valence electrons in pairs so that each atom is bonded to all neighboring atoms.

4. Complete the outer shells of the atoms bonded to the central atom.

5. Place the rest of the electron pairs on the central atom.

6. If necessary, form multiple bonds so that each atom has a filled outer shell.