Lewis diagrams are a way to show us the amount of valence electrons are arranged for a molecule/ion.
They specifically show us the following:
- Bonding pairs
- Non-bonding pairs
- Satisfaction of the octet rule
- Shape (using VSEPR)
Lewis diagrams are easy to draw, as long as you know how many valence electrons the molecule/ion has, however, it is easy with the periodic table.
Look at the group number of the ion/molecule. If, for example, sodium, is in group 1, so therefore it has 1 valence electrons. Likewise, berylium, has 2 since it’s in group 2.
For ions/molecules that’s in group 13~18, use the last digit. For example, carbon is in group 14, so it has 4 valence electrons. Likewise, oxygen is in group 16, so it has 6 valence electrons.
To draw the actual diagram, Write the symbol of the ion/molecule in the center. Then, place the valence electrons around the atom. For lewis diagrams of 2 or more ion/molecule, the goal is to ‘get a full outer shell’. This is usually 8, but there are some exceptions such as Hydrogen (2) or Boron (6).
If all the ions/molecules are with full valence electron shells, then the lewis diagram is complete.
When you ‘bond’ (connect) the ions/molecules in lewis diagrams, you can use a line, instead of 2 dots in between the ions/molecules. However, if it’s NOT connected, you MUST use dots.
Drawing them is pretty self-explanatory.