Chem Standard 2E

Objective: Students know how to draw Lewis dot structures.

Drawing Lewis dot structures really isn't too complicated, once you know the steps.

1) Find the total number of valence electrons in the molecule.


Here's a table with some common individual structures.


2) Figure out how many octet electrons the molecule should have, using the octet rule(all atoms want eight valence electrons to be like the nearest noble gas). Use this rule to figure out how many electrons each atom in the molecule should have, then add.
*There are two that do not want eight, being Hydrogen (2) and Boron (6).

3) Subtract the valence electrons from octet electrons [Subtract the answer from number one from number two]. The answer will equal the number of bonding electrons in the molecule.

[Divide the number of bonding electrons by two because every bond has two electrons, thus the # of bonds in the molecule = number of bonding electrons/2]

4) Draw an arrangement of the atoms for the molecule that contains the number of bonds you found in #4 above.

Here are some helpful guidelines:

o Hydrogen and the halogens bond once.
o Oxygen and its family bond two times.
o Boron itself and Nitrogen's family bond three times.
o Carbon and its family bonds four times.

A good thing to do is to bond all the atoms together by single bonds, and then add the multiple bonds until the rules above are followed.

5) Finding number of lone(nonbonding) electron pairs by subtracting the bonding electrons (#3) from the valence electrons (#1). Arrange these around the atoms until they satisfy the octet rule.

--> Then you're done with drawing those Lewis dot structures!

A fine example of drawing a Lewis Dot Structure, specifically - Carbon Dioxide.