I talk too much, so here’s the lesson. Straight up.

Steps for Writing Lewis Dot Structures

1. Draw the molecular skeleton. As a rule of thumb, H atoms are always on the ends and the least electronegative atoms are in the middle.
2. Calculate the total number of VALENCE electrons that will be in the final molecule. You can do this by adding the group numbers of each atom together.
3. Distribute the electrons among the atoms. Start with the bonding atoms (2 electrons per bond) and then go back and fill in octets and duets where needed. Make sure you don’t add any more electrons than the number you calculated in step 2.
4. Make double or triple bonds when necessary. If any atom does not have a full octet, share a pair of electrons from a nearby atom in order to form a double or triple bond so that each atom can have a full octet.

Example: Sodium Fluoride

First, we’ll need to figure out the skeleton for NaF. Since there are only 2 atoms, there’s no need to consult a periodic table for electronegativity.

Next, we’ll need to add together the valence electrons to find out exactly what we’re working with here. Since Sodium is a Group 1 atom and Fluorine is a Group 7 atom, we know that the total number of valence electrons is (1+7)=8.

Now that we know how many electrons to work with, we’ll start by adding our bonding electrons.This leaves us with 6 electrons to distribute.

Distributing these last six electrons doesn’t give us enough to complete an octet.

So, let’s share the electrons so that we end up with two full octets. This means that we’ll have to use a double bond.

Best of Luck,

Grey