You may be asked to draw electron dot structures of molecules that are ions or molecules that have a charge. The steps are similar to covalent bonding for non-ions, but there are some slight adjustments you must make. Let’s look at an example of a common anion.

First, use the periodic table to help you.

Now, let’s draw the covalent electron dot structures for nitrate. The chemical formula for nitrate is NO₃^-1. (Notice the one negative charge on nitrate.)

Click on the Next button to begin the interactive.

Watch the following video to see the drawing of a positive polyatomic ion or cation.

It is important to note that some elements can have an expanded valence (more than eight electrons in the valence shell) while some elements like boron and beryllium can have fewer than an octet. (B: 6 electrons, Be: 4 electrons). These elements will always be your central atoms. Allow them to be strange, and let the formal charges guide you. Most atoms will have a complete valence shell with eight electrons.

Watch the following video to see an example of an expanded valence. You only need to watch the first minute and 52 seconds of the video.

Watch the following video to see an example of drawing an electron dot structure where there are less than eight electrons in the valence shell.