Is it an Azide or Nitride ion? Ionic vs. Covalent Compounds

The problem: Sometimes an azide compound might look like a nitride compound at first glance!

I have a coloring worksheet that many middle school and high school teachers use to introduce or review ionic and covalent compounds. It's great because students color metals gray, nonmetals red, and polyatomic ions blue. This gives them a visual reinforcement that ionic and covalent compounds aren't just randomly established. There are rules. Using colors just makes it a little more fun! However, I get a few questions that come up on a regular basis that I'd like to clear up here.

I think the nitride ion has the wrong charge...

This is a very common question and it is easy to mistake the azide ion for the nitride ion! I try to raise the bar in all of my worksheets even if it is something simple like a coloring worksheet. I decided to include the azide ion to try to raise the bar on this worksheet. The azide ion has a charge of negative 1, whereas the nitride ion has a charge of negative 3.  I think since we use nitride so much more than azide, it is easy to read through too quickly and assume it is the ion we are more familiar with.

Some might like a more detailed reason as to why azide has a charge of negative 1 and that has to do with how you calculate the formal charge. You can read that post here.

What is the difference in chlorine dioxide and chloride peroxide?

Some of the teachers who use this worksheet take it a step further and ask the students to name the compounds after they color them. What a great idea! Because of that great idea, some have asked me what the proper name is for ClO ₂.

 Chlorine Dioxide vs. ​Chlorine Peroxide

Chlorine dioxide is two nonmetals, so it has to be covalent. This is actually the compound featured on the worksheet.

It would be very easy to mix up chlorine peroxide for chlorine dioxide. What you need to remember is that if it was peroxide it would likely be ionic. If it was ionic, the charges would have to balance and the compound featured above would not have balanced charges because they are both negative. This compound is actually a dimer and from here I would have to go into organic chemistry and nobody wants that. 

​I hope this helps you use the ionic covalent bond worksheet better!