How Do You Figure Out the Charge on the Azide Ion?

The Problem: Many high school courses don't have time to go over formal charge, so you may need a refresher.

This is a complimentary post in order for you to understand more about the azide ion. To check out the ionic/covalent worksheet where this ion was introduced click here, or read the blog post of frequently asked questions here.

Let's calculate the formal charge on the left nitrogen

1) Calculate the number of valence electrons in a neutral atom. In this case it would be 5, which you find that number based on the column number nitrogen is in. 2) Subtract half of the number of bonding electrons. There are 4 bonding electrons, and half of that would be 2. 3) Subtract the number of nonbonding electrons. There are 4 bonding electrons, so you would subtract 4. Finally, 5 - 2 -4 = -1. So the charge on this first nitrogen would be -1.

Let's calculate the formal charge on the center nitrogen

1) Calculate the number of valence electrons in a neutral atom. In this case it would be 5, which you find that number based on the column number nitrogen is in. 2) Subtract half of the number of bonding electrons. There are 8 bonding electrons, and half of that would be 4. 3) Subtract the number of nonbonding electrons. There are 0 bonding electrons, so you would subtract 0. Finally, 5 - 4 -0 = -1. So the charge on the central nitrogen would be +1.

Let's calculate the formal charge on the right nitrogen

1) Calculate the number of valence electrons in a neutral atom. In this case it would be 5, which you find that number based on the column number nitrogen is in. 2) Subtract half of the number of bonding electrons. There are 4 bonding electrons, and half of that would be 2. 3) Subtract the number of nonbonding electrons. There are 4 bonding electrons, so you would subtract 4. Finally, 5 - 2 -4 = -1. So the charge on this first nitrogen would be -1.

So, overall the left nitrogen is -1, the central nitrogen is, +1, and the right nitrogen is -1. If you add all that up, you get an overall -1 charge, and that is why azide has a -1 charge.

If you'd like to see this in a video form, check out this link.

Or, if you'd like to use the ionic covalent coloring worksheet with your high school, middle school, or homeschool chemistry students, go here.