This is an introduction to naming ionic compounds with transition metals. The transition metals are the elements in this part of the periodic table, and when we write the name for an ionic compound that contains transition metals, those names usually have Roman numerals in the middle of them. So in this video, we'll learn how to take the formula for a compound that contains a transition metal and how to write the name for it with Roman numerals and everything. So transition metals.
The transition metals are the elements in this part of the periodic table here and I've written in some of the most common. I'm also going to be talking about some of the metals over here which aren't technically transition metals but they act a lot like. These metals are unique because many of them are able to make multiple ions with different charges. So iron, Fe for example, is able to make an Fe2 plus ion.
but it's also able to make an Fe3 plus ion. Okay this is different from the metals say over here that tend to always make ions with the same charge. Sodium for example is in this plus one column here and so when sodium is in an ionic compound it always makes an ion with a one plus charge.
Magnesium here is in this two plus column so when it is in an ionic compound It makes a 2 plus ion, but the transition metals can make a wide variety of different ions with different charges. Some of them can even make 4 or 5 different ions, each with a different charge. So these different charges on transition metals really come into play when we want to name a compound that contains a transition metal.
So here we have FeCl3, and for the Fe, the iron, we can't tell right away just by looking at this. whether the Fe is Fe2+, or whether it's Fe3+. We have these two different types of ions that Fe can make. Now, we can distinguish between these two ions by using Roman numerals to give them different names.
So the Fe2+, we call that iron 2, with the Roman numeral for 2 in parentheses. The Fe3+, we call that iron 3. with the roman numeral for three in parentheses and we'll use these ion names when we want to name the whole compound so if the fe here turns out to be fe2 plus we'll call this compound iron two chloride and if this iron is iron three plus we will call the compound iron three chloride so in order to figure out whether we're talking about iron two chloride or iron three chloride here we got to do a little bit of math and work backwards to figure out which of these two charges iron has in this particular compound let me show you how to do it so to find the charge of a transition metal we start by focusing on the ion with a charge that we do know that's certain that's not going to change and for this that's going to be cl cl is in this column here on the periodic table so we know that in an ionic compound Cl always makes an ion with a 1-charge. Okay, so we've got Cl1-.
Now, how much total negative charge do we have here? We have three Cls, so that's going to be 1, 2, 3. And since we have three of them, the total amount of negative charge is going to be 3-. Now, in an ionic compound, the negative charge always has to balance out with a positive charge.
So if we have 3 minus on this side, we've got to have 3 plus on this side. So what's the charge on iron? Well, there is one iron ion in this compound, which means that all of the positive charge has to be on this one ion, which means that its charge is Fe3+. So one... Ion of Fe3 plus gives us 3 plus of charge, which has to be balanced out by the 3 minus over here, which is distributed over the 3 Cl minuses.
So that's how we figure out the charge on iron. And since this is iron 3 plus, the name for this compound is going to be iron 3. And then for Cl, when Cl, when Cl. Chlorine becomes a negative ion. We call it chloride, the I-D-E.
usually gets added to the name of an element when it becomes a negative ion. So chloride is what we call Cl1-. So iron 3 chloride is the name of this compound. We had to work backwards and figure out the charge of iron, and then we can call it iron 3. So if you want to get really good at naming compounds with transition metals and using the Roman numerals and all that, you've just got to get a lot of practice.
So I've made another video that's just a whole lot more interesting. whole bunch of practice problems on naming ionic compounds with transition metals. But before you check that out I want to talk about a couple of important things. The first thing I want to talk about is when we use roman numerals for naming and when we don't. This confuses a lot of students.
Okay so when do we use roman numerals? Well we use roman numerals when we're naming compounds that contain transition metals. So here are three compounds that contain transition metals.
And as you can see, we use these Roman numerals. And we use the Roman numerals because copper, iron, and vanadium are transition metals, which means that they can make multiple ions with different charges. So we kind of need to pin down the specific ion that we're talking about in each one of these compounds, right? So we put this one here to say we're talking about copper 1+, because copper could make other ions. We're talking about iron 3+, here.
We're talking about vanadium 4+, because they could be a variety of different ions. Now, on the other hand, we don't use Roman numerals when we're naming compounds that don't contain transition metals that contain, for example, the metals over here. Take potassium iodide, for example. Potassium, K, is in this column. It's in the 1 plus column, which means that in an ionic compound, potassium always makes an ion with a 1 plus charge.
That's the only choice. It can only be 1 plus. So we don't need to put a Roman numeral in there to specify that it's 1 plus because that's the only choice that it could be. Calcium nitride over here, calcium is in this 2 plus column and it can only make an ion with a 2 plus charge in an ionic compound.
So again, we don't need a Roman numeral to say that because there's only one choice and that's 2 plus. Now aluminum over here can only make a 3 plus ion so you don't need to use roman numerals with aluminum either. And I should point out that some of these metals here that are not technically transition metals still can make ions with different charges so we have to use roman numerals when we name compounds with tin and lead in them as well. But here's the big point.
If you're naming compounds with ions that can make different charges you always need the roman numerals. So don't put those roman numerals in. If you're naming compounds with metals that can only make one charge, not only is it a waste of time to put those Roman numerals in, but it's wrong.
You just shouldn't put them in there. Now we have to use this method of working backwards in order to name compounds that contain most transition metal. And we also have to use this method to name compounds that contain metals like tin or lead that are able to make more than one type of ion. But there are... two important exceptions that I need to tell you about.
And these are silver, Ag, and zinc, Zn. Even though these two elements are transition metals, they're only able to make one type of ion. So silver, Ag, always makes Ag one plus.
It's always one plus and only one plus. Zn, always makes an ion that is Zn2+. Now, that means that when we name compounds that contain silver or zinc, we don't have to use Roman numerals, because we're only talking about one type of ion, okay?
So a compound like this, AgCl, you don't have to do any math at all, you don't have to use a working backwards approach, you just call it silver chloride. ZnCl here, super easy. We just call that zinc chloride. And since these elements always make ions with just one charge, we don't have to use the Roman numerals when we're naming them.
So it would be wrong to call this silver chloride or zinc chloride here. There's only one possible ion, so we don't use the Roman numerals. We only use the Roman numerals if we're trying to distinguish between multiple types of ions with different charges.
So that's an introduction to how we name compounds that have transition metals. In the next video, we'll do a whole bunch of practice problems so you can really get the hang of it. This is one of the things that you just get better and better at with more practice.
So check out that video. You'll get super good at it really fast.