 Welcome, my name is Brad Langdell. I'm going to talk to you about Ionic nomenclature. Nomenclature? Why would you give it such a big complicated hard to spell word? It just means naming things, writing the name out or writing the formula out. We're going to be doing both of those today for three types of Ionic compounds. Binary, which is the easiest. Multivalent, which is a little trickier. And then polyatomic, which is the trickiest one I think it is. That's what kids tell me. I hopefully think you will find them all pretty easy. Here's what you need. Question. I'll give you lots of questions. You don't need to worry about that so much. You need a periodic table. This is so important. You need a periodic table. Every time you're doing nomenclature it will make your life so much easier. And carefulness. Just go carefully and slowly through these and they can be pretty easy to do. And you'll get good at it eventually. Watch. Binary Ionic compounds. Binary because they're made up of just two different types of elements. A metal and a non-metal. When we're writing these, we're going to start with the metal. So here we have an example. SRCl2. The first part, the SR is the metal. You look on your periodic table and you find out that SR is strontium. So I'm going to route down. Strontium. Then I look at the second part. CL. That is chlorine. But here's the thing. I'm not going to write chlorine. I'm going to write chloride. I'm going to change the suffix, which is the ending of the non-metal to chloride. Do I do anything with that too? No. Not yet. Do I do anything with that S? No. Not yet. I'm finished. I'm good. That's the basic just naming of SRCl2. You would say that out as strontium chloride. Simple. Now let's go the other way around. Let's say I want to write the formula. Well, I'm going to have a metal and a non-metal again. I'm going to use my periodic table. So for aluminum, I look on my periodic table. There it is. It's AL. And for sulfide, I'll look on my periodic table. The nice Science 10 periodic tables even have sulfide on there. It's about a little differently, but that's okay. And so I know that that's an S. Now what I need to do is go through and take a look at those charges. I have to cross the charges. This is so important when I'm writing the formulas for binary ionic compounds. So what I'm going to do is look at the charge on aluminum. It is a 3. I'm going to take that 3 and I'm going to cross it over to the sulfur. And I'm going to take the 2 which was on the sulfur and I'm going to put it over on the aluminum. You see the sharing? It's so nice. So aluminum sulfide, AL2S3. Notice that 3 does not go on the aluminum. It goes over to the sulfur. And same thing. The sulfur's 2 goes to the aluminum. It's like a trade. It's great. Why does it work that way? Well, you can go and check out some other videos about that. You'll learn about that in Chemistry 22. But if you're just wanting to get the naming down, that's what you do. Well, this is kind of weird. What if you had something like magnesium oxide? Magnesium Mg has a charge of 2 plus and oxygen O has a charge of 2 minus. So if you cross the charges, I guess they'd both be 2s. But in chemistry, we don't bother writing that. If they're both the same, we just ignore it. By the same token, if you had 2 that were the same like element X and Y, maybe they weren't the same. Maybe one was like 3 and the other one was 6. You would still kind of reduce this down so that one now became 1 and one became 3. And then you wouldn't actually write the 1. We just reduce down any time that we can. That doesn't come up very often. And mostly it's choose but good to know anyways. There's always exceptions in chemistry, which is why it's not as cool as physics. Multivalent ionic compounds. It's a little bit harder now. So have you ever seen a periodic table? There's the odd element. In fact, there's a lot of them. Where they have more than one charge? Yeah. How do you deal with those guys? You're going to use Roman numerals. So take a look at this example. We've got tin sulfide. Okay, so that's not so bad. I know it's tin. I know it's sulfide. You could write that pretty easily. But which tin are you talking about here? Are we talking about the tin that was tin 4? Or are we talking about the tin that was tin 2? Because there's two kind of varieties or two flavors of tin. So think about it. Look at the formula. S-N-S. Okay, there's no 4 in there anywhere. So it wasn't tin 4 we were talking about. Then I know what you're thinking. You're saying there's no 2 in there either. But remember we talked about with magnesium oxide a second ago? The 2 and the 2, they cross over and they cancelled out. So this must have been tin 2 sulfide. And you have to put that 2 in there. That is important. If you don't have it in there, yeah, you'll probably get marks taken off of your work. Because it's a different compound from tin 4. And there's no such thing as just tin sulfide. It's got to be tin 2 or tin 4. Notice we still kept the i at the end. There's no real change there. What if we're going the other way around? It's actually pretty easy. It will tell you which elements you're going to use. Are you going to use the chromium 3 or the chromium 2? Chromium 3. So I'm going to go through and I'm going to write chromium, which is CR. I'm going to write oxygen, which is O. And I'm going to cross the charges. Still cross the charges for these multivalent ionic compounds. So the chromium has a 3 that goes next to the oxygen. And the oxygen has a 2 that goes next to the chromium. There's chromium 3 oxide. Now for the last type here, we're going to look at polyatomic ionic compounds. These are a little bit tricky. Sometimes kids will get to these and they'll get really intimidated because look at all of the different elements. In fact, there's three elements in the particular example I pulled out here. It's kind of like people with three names like, you know, Robert Downey Jr. I always think that, you know, that's kind of weird. He's got three names, three parts. It's a little more complicated, but it's not that bad. The main thing you want to remember is that this is not sodium sulfur oxide. You have to actually go and look up what the name of this ugly S203 thing is. It's a polyatomic ion and it will be in your table of polyatomic ions, which is found on your periodic table. So let's start off naming this with the sodium. The sodium part we can do, that's easy. Na is sodium. There it is on my periodic table. I could find that pretty easily. Now S203 you're going to look through this table of polyatomic ions. Just go through the rows. Eventually you'll get there. Oh, there it was pretty much at the end. This is thiosulfate. And it's as simple as that. You just write it out. You just have to find it on the periodic table. It's S203, 2 negative, and that's where the 2 came from here in the sodium. Sodium is a charge of 1, so it crossed over. We didn't write the 1 in. It's simple, just like that. Now the thing that makes it hard for kids is they forget to look at the table. So keep your periodic table out anytime you're not sure about an element, look it up and see if it's in the polyatomic table of ions. If it is, then it's an easy one to go through and solve. Alright, one more here as we go the other way. What if I had something like ammonium sulfide? A lot of kids will try to not know what ammonium is and they'll just make something up. Well, look on your table. There's ammonium. It's a polyatomic ion, NH4 positive. So I'll start off with NH4 positive. And sulfide we know is S, that's 2 negative. So the positive goes down here to the sulfur. We don't put the 1 in though. And the 2 negative from the sulfur goes over here to the ammonium. So there's ammonium sulfide. Now there's one extra thing we get to do here. Anytime you've got a polyatomic ion and you've got more than one of them, you're going to put it in brackets. That way we know that there are two of the ammoniums and not like one nitrogen and eight hydrogens, which is what it would have been otherwise. Or maybe 42 because we had a 4 and a 2 right next to it. So put it in brackets. Now if you're looking for a few more things to watch about ionic naming, there's a great crash course chemistry video out there from Hank Green. He does a good job of talking about how to speak chemistrarian. As crash course number 11, I'll leave a link in the description. And you can check out my website www.ldindustries.ca for lots more examples and notes you can use to learn your nomenclature. Good luck.