Step 1: Arrange the atoms in the correct layout (i.e., bonding arrangement). The layout is experimentally determined, but can often be deduced from the formula for the molecule (or ion). For many molecules (but NOT all!), the first listed atom is in the center, and the others are attached to it.

Step 2: Count the number of valence electrons in the molecule by summing the electrons contributed by each atom, based on their group numbers. If the molecule is negatively charged, add the corresponding number of electrons. Subtract the appropriate number of electrons if the molecule is positively charged.

Step 3: Develop a trial structure for the molecule by putting a single bond (1 electron pair, represented by a single line) between each pair of bonded atoms. Then complete the octets of as many atoms as possible by adding nonbonding electron pairs (often called lone pairs) to the atoms in turn until all of the available valence electrons (step 2) have been used.

Situations will arise in which electrons remain to be added to the structure after the octets of all atoms are complete. In these situations, the remaining electrons are placed in pairs on the central atom.

Step 4: Examine the trial structure. If all atoms have octets (or if the terminal atoms have octets while the central atom has more than 8 electrons), the trial structure is acceptable. If the trial structure shows atoms with fewer than eight electrons, it must be altered by using lone pairs to form multiple bonds until all atoms have octets.

ONCE THE CORRECT NUMBER OF ELECTRONS IS PLACED IN THE STRUCTURE IN STEP 3, NO MORE MAY BE ADDED, AND NONE MAY BE REMOVED; electrons can, however, be MOVED.