For this one, it says determine the number of ligands in the complex ion. Now, remember, the complex ion portion is the part that is within the brackets. That fluoride is a counter ion because it's outside the brackets. So fluoride is in group 7, so its charge is minus 1. So to have an overall neutral coordination complex, that means it has to be plus 1. So that plus 1 and that negative one cancel out, and that's why the coordination complex overall is neutral.

Now, we're going to say within this complex ion portion, we see that chromium is our transition metal and it's connected to what appears to be 4 water molecules and 2 bromide ions. So that is a total of 6 ligands that are attached to my chromium ion. So that would be our answer.

Now, I didn't ask for the charge of the chromium, but let's take a look at it and see if we can figure it out. So here, the bromines each have a charge of minus 1. Together, that would mean that they're minus 2. But our complex ion's charge overall is plus 1. This could only happen if the chromium itself was plus 3. Because we have plus 3 minus 2 gives me plus 1 overall. Remember, water molecules are neutral, so they don't contribute to the charge at all.

Alright. So just remember, when it comes to a coordination complex, you have to be able to spot the complex ion portion and the counter ion portion. You may also be asked to look at the complex ion and break it down a little bit further into its ligand portions and its transition metal portion. And when it comes to our ligands, it's normal to see 2, 4, or 6 of them connected to our transition metal. Now that we've seen this, click on to the next video where we dive a little bit deeper into the different types of molecular geometries that are possible based on the number of ligands attached to my transition metal.