Understanding Ionic Compound Naming

Let's have a look at how we name molecular compounds starting off with ionic compounds to begin with. You see many substances have common names but they don't tell you what's really inside of them. Some of these names are very very old so take for example Epsom salts. His formula is actually MgSO4. He's known as magnesium sulfate. and that is the IUPAC name for that compound and that stands for the International Union of Pure and Applied Chemistry these are the people who make sure that we're all using the same rules to name our compounds if we have a look at an ionic bond it's pretty straightforward to understand it here's a sodium atom over here and he's got this one solitary electron in his outer valence orbit and he would love nothing better than to get rid of it over on the right hand side we have chlorine and it's got a vacancy for one electron. That would complete the outer valence shell and have a total of eight and he'd love to do that. So this is kinda like a match made in heaven. What happens is the sodium gives his electron to the chlorine and so the sodium ends up being 11 positives in his nucleus. He's got 11 protons but now he's only got 10 electrons so overall he's got a charge of one plus. Meanwhile the chlorine had 17 protons in his nucleus and he's now got 18 electrons because he picked up an extra one, and so he's got a charge of one negative. And so this is what goes on in an ionic bond. One gives an electron, one takes it. If we have a look at how we name it, it's fairly straightforward. We name the cation, or the metal, first. So this is coming from the right-hand side of the periodic table. And we name the anion, or the nonmetal, second. And this is coming from the left-hand side of the periodic table. We also change the ending of the name of the anion to "-ide". So let's have a look at here. We've got a formula KCl, and K stands for potassium. That's because the ancient name for potassium was kalium. The anion in this formula is chlorine. And so when we name this, we keep the first name. The metal stays the same. So it stays as potassium. We don't change that at all. But the second name gets changed to chloride, and there's that ide ending that we change it to. Next up, we have a combination of calcium and iodine. So we have calcium as the cation. This is the metal, positively charged. And the negative one is iodine. So when we name it, we keep the first name the same, calcium. That doesn't change at all. I-O, and here we change the ending, ide, iodide. We have sodium and nitrogen. So we have sodium and the symbol is Na because his old name used to be Natrium. And we have nitrogen. Now we keep the first fellow with the same name. So sodium keeps his name without changes. Nitrogen becomes Nitride. Sodium Nitride. Let's have a look at writing the formula. So if we give you the name, how would you write the formula? Well, we've got to look up the name. So we have sodium chloride. Sodium, as we've already figured out, the cation is, the symbol for it is capital N and a little a. Chloride comes from chlorine, Cl. Now, what's the ratio between these? Well, if you look on the periodic table at sodium and chlorine, you'll see that sodium is typically a single positive. Chlorine is a single negative. one of each. So a ratio of one to one, one each will do it. So the formula comes out being one sodium, one chlorine, and we're good. That's a perfect match. What about barium fluoride? Well, the symbol for barium is big B, little a, and you'll see that barium typically has a charge of two positives. We're going to connect that to fluorine, whose symbol is a capital F, and he has a single negative. All right, now this is an imbalance here. To make this work, I'm going to need two fluorines for every barium. So for every one barium, I'm going to need two fluorines. So the formula for this one will be Ba, a single Ba, and to get two fluorines, I'll put a subscript after it. So it's BaF2, potassium nitride. All right, potassium is K, and the typical charge on potassium is it has a single positive. We're going to combine that with nitrogen. Symbol is capital N, and the typical charge on this guy is three negatives. All right, now to make this thing work, I'm going to have to have three. potassiums to equal just one nitrogen. And so the formula is going to be K3N. And there's how we get our 3 to 1 ratio using subscripts. Aluminum chloride. Alright, aluminum is capital A, L, and he's typically 3+. Chloride, we've already done this one, capital C, L, and one negative. Now to make this work I'm gonna have to have three chlorines. for every one aluminum. So for every one aluminum, I'm going to need three chlorines. So the formula is going to be AlCl3. Barium nitride. All right, we've been there before. Barium is two pluses. Nitrogen is three minuses. Okay, now this is weird. Twos and threes. Well, let's think of mathematics and doing some factoring here. Two times three gives you six. So think of this very carefully. If I take three bariums, now that's three times positive two, that'll give me positive six. And if I take two nitrogens, that's two times negative three, that'll give me negative six. Right, three times two, two times three, they both equal six. So to make this ionic bond work, I'm going to have to have barium, three of them, and nitrogen. two of them, so the formula is going to come out being Ba3N2, and now their pluses and minuses will equal each other. There is a bit of a problem with some of our metals on the periodic table. Some of them have more than one stable ion, so for example, iron has two. It can be iron with a two-plus charge or iron with a three-plus charge. Well, how are we going to tell them apart? It's actually pretty easy. We put a Roman numeral after it, so iron 2 means iron with a two-plus charge, and iron, Roman numeral 3, means iron with a 3 plus charge. So here, for example, in the first row, I've got iron 3 chloride. So what does that mean? Well, it means the cation is iron with the 3 plus. That's what the Roman numeral 3 means. And, of course, chlorine is Cl, and we know that it has 1 minus. We've seen this before. So to make this work for every 1 iron, I'm going to need 3 chlorine. So the formula is going to have to be, for every 1 iron, I need three chlorines. It's FeCl3. What about this next one? I've got lead oxide. All right, so it's made up of lead, Pb, and oxygen, O. Now, lead can come in two different varieties. Sometimes lead can be plus two. Sometimes it can be plus four. Which is it? Well, to figure that out, we're going to have to have a look at the oxygen. You see, the oxygen is always going to be negative two. There's no getting around that one. And you'll notice that over here on the formula, I've got two oxygens. And so 2 times negative 2, what I've actually got over here is I've got a total of negative 4, right? Because I have two oxygens in the formula. So if I've got a total of negative 4 charges, what lead must it be? Well, you've probably guessed it. It's going to have to be the lead with the 4 plus, so that 4 pluses match up with 4 negatives. So this guy is going to be called lead. Which lead? Lead IV, Roman numeral IV, and then of course comes the oxide, changed into IDE. Nickel III sulfide. Well, nickel is capital N little i, and it's nickel with three positive charges. Sulfide is a capital letter S, and sulfide has a charge of negative 2. So to make these guys work, here's the twos and threes making six again. So I've got to try and make 6 out of the deal. So for the nickel, I'll multiply that by 2, because 2 times 3 pluses is 6 pluses. And for the sulfur, I'll multiply this one times 3, because 3 times negative 2 is negative 6. So now my charges match. So you probably see it's pretty easy going from the name to the formula, because the name tells you which metal to use. This next one, we're going to go from the formula to the name. I know I'm going to use copper. and I'm going to use fluorine. And I've got two of these fluorines, and I know that each fluorine is negative, and I know that I've got two of them here. So what I've got is, I've got a total of two negative charges all together with my fluorine. So what copper is going to match that? Well, according to the formula here, I've got to come up with a charge of two. So I'm going to use the copper two. I'm going to use the copper two plus, so that my two pluses match my two negatives. And so I'm going to call this fellow copper 2. I'm going to use the 2 plus and fluoride. Now when you spell fluoride, be careful, okay? It's not flower, it's fluoride. So use a U-O-R-I-D-E. A lot of kids spell it like flower-ide. Chromium 3 sulfide. Now I'm just going to erase some of the... line I made here, so I've got some space to work in. Chromium 3. Well, the symbol for chromium is capital C, little r, and he's chromium with three pluses. That's this one over here, as opposed to chromium with two pluses. And then sulfide, sulfur is two negatives. Now, here we go again, twos and threes. So we've got to make six out of the deal. So I'm going to take the chromiums, which is three plus, and I'm going to multiply it by two. That'll give me six. and I'm going to take the sulfur, which is two negatives, and I'm going to multiply it by three. So it's Cr2S3, and we got that guy worked out. FeO, that's an iron, and that's an oxygen. But again, which iron? Is it the iron 2 plus or the iron 3 plus? Well, again, look at the oxygen. The oxygen is two negative. That's all he can be. So I've got to make sure if it's one of each, then this guy must be two positives. So two positives make it. balance two negatives. So the iron I'm using is the iron I'm using iron oxide. This is how you deal with handling multi-valent metals that have more than one possible charge. You need to use their partner to figure out what charge they are and the charge is written in the form of a Roman numeral. Last but not least you may have to deal with polyatomic ions. This is a group of non-metals that are clustered together. They operate as a unit. So polyatomic just means many atoms, and they work together. So for example, here's one, the hydroxide iron, which is OH-, made of one oxygen and one hydrogen, and it always works together as one. They don't separate. They go together as a team. You can see a list of this on page 44 or on your periodic table in your science data booklet. They can often be recognized by their endings. Look for words that have 8. or ite. So you've already seen ide, I-D-E, that means it's periodic table. If you see ite or ite, you want to look on the chart of polyatomic ions. Well let's do a few. Barium hydroxide, so the cation is barium, Ba, and hydroxide, well that's an OH. And you can find that on your periodic table if you look at your polyatomic ions. And if you do a little bit of searching and hunting, you should eventually figure out where is that thing. is OH. There he is. Now an OH typically has one negative charge, but if you recall, barium has two positives when you look him up on the periodic table. So if you're going to make this work, for every one barium, you're going to need two hydroxides. So here's my barium. Now I need two hydroxides, but they've got to be kept together as a unit. So here's O and H, and then I place brackets around the two of them to keep them together. Then I put my subscript. Now these brackets are incredibly important. If I don't have that subscript, I'll have BaOH2, and that means all I've got is two hydrogens. But I need two OHs, not just two hydrogens, so the entire polyatomic ion must be bracketed. Iron 3 carbonate. Sorry, that means I'm going to use iron with the 3 plus charge. And carbonate. Okay, well what the heck is a carbonate? Well here he is down here. Carbonate is C. CO3 and he's got a charge of negative 2. So I've got plus 3's and negative 2's. I'm going to make 6 out of this deal. So I'm going to take the iron, which is plus 3, and I'm going to multiply that by 2. And I'm going to take the carbonate, which is CO3, and I'm going to multiply that by 3. But I got to do the whole thing. So I put brackets around the entire unit and then I multiply that by 3. And that's how we deal with that. Copper 1 permanganate. Copper is Cu, and the 1 means it's 1 plus charge. Permanganate. Okay, well, what is a permanganate? Here it is. He is capital M, little n, there's your manganese, O4, and he has a negative charge. So this is rather interesting. It looks like one copper will be perfectly balanced by one permanganate. So he's going to be CuMnO4. Put them all together. We don't need any brackets because it's one of each. Everything's just fine. Now here I have the formula. I've got gold, AU, and I've got nitrate, which is NO3. Now it says I've got three nitrates, so that's kind of curious. Why is that? Well, if I look up my nitrate on the chart of polyatomic ions here, where is my nitrate? Here we go. I kind of cut it off here. Nitrate is NO3 and it has a charge of negative 1. And it's saying over here that I've got three of them. So if I've got three of these negative 1s, then the gold must be three positives. All right, so three positives will balance three negatives. And so what have I got here? I've got gold, three, and I've got, now watch the spelling, NO3 is nitrite, I-T-E. Nitrate is NO4. Here's one that's made of two polyatomic ions, this one here and this one here. NH4 is known as ammonium. I don't know if I'm going to get it all in here. and P04 is known as phosphate. So what I've got here if I put them together, I've got ammonium phosphate. And we need three ammoniums to go with that phosphate. Reason why is because ammonium only has a charge of a single positive, just one positive, but a phosphate is worth three negatives. That's why I need three ammoniums to work with that one. Here's an interesting one. I've got K. Now, I know what that is. That's potassium. And then I've got Cr2O7. Well, that guy's called dichromate, and he typically has a charge of negative 2. So Cr2O7. This whole thing is worth negative 2. Potassium, if you recall, is worth a positive 1. That's why I've got to have two potassiums to match that dichromate. I need two of them to equal the negative two charges on the dichromate. And so what's this fellow going to be called? He's going to be simply called potassium dichromate. And so this will hopefully help you realize that when you've got a polyatomic ion, use this little chart that's on your periodic table and let that help you find the names of these fellows.

and that is the IUPAC name for that compound and that stands for the International Union of Pure and Applied Chemistry these are the people who make sure that we're all using the same rules to name our compounds if we have a look at an ionic bond it's pretty straightforward to understand it here's a sodium atom over here and he's got this one solitary electron in his outer valence orbit and he would love nothing better than to get rid of it over on the right hand side we have chlorine and it's got a vacancy for one electron. That would complete the outer valence shell and have a total of eight and he'd love to do that. So this is kinda like a match made in heaven.

What happens is the sodium gives his electron to the chlorine and so the sodium ends up being 11 positives in his nucleus. He's got 11 protons but now he's only got 10 electrons so overall he's got a charge of one plus. Meanwhile the chlorine had 17 protons in his nucleus and he's now got 18 electrons because he picked up an extra one, and so he's got a charge of one negative. And so this is what goes on in an ionic bond.

One gives an electron, one takes it. If we have a look at how we name it, it's fairly straightforward. We name the cation, or the metal, first. So this is coming from the right-hand side of the periodic table. And we name the anion, or the nonmetal, second.

And this is coming from the left-hand side of the periodic table. We also change the ending of the name of the anion to "-ide". So let's have a look at here.

We've got a formula KCl, and K stands for potassium. That's because the ancient name for potassium was kalium. The anion in this formula is chlorine. And so when we name this, we keep the first name. The metal stays the same.

So it stays as potassium. We don't change that at all. But the second name gets changed to chloride, and there's that ide ending that we change it to.

Next up, we have a combination of calcium and iodine. So we have calcium as the cation. This is the metal, positively charged. And the negative one is iodine.

So when we name it, we keep the first name the same, calcium. That doesn't change at all. I-O, and here we change the ending, ide, iodide. We have sodium and nitrogen. So we have sodium and the symbol is Na because his old name used to be Natrium.

And we have nitrogen. Now we keep the first fellow with the same name. So sodium keeps his name without changes. Nitrogen becomes Nitride. Sodium Nitride.

Let's have a look at writing the formula. So if we give you the name, how would you write the formula? Well, we've got to look up the name. So we have sodium chloride.

Sodium, as we've already figured out, the cation is, the symbol for it is capital N and a little a. Chloride comes from chlorine, Cl. Now, what's the ratio between these?

Well, if you look on the periodic table at sodium and chlorine, you'll see that sodium is typically a single positive. Chlorine is a single negative. one of each. So a ratio of one to one, one each will do it. So the formula comes out being one sodium, one chlorine, and we're good.

That's a perfect match. What about barium fluoride? Well, the symbol for barium is big B, little a, and you'll see that barium typically has a charge of two positives.

We're going to connect that to fluorine, whose symbol is a capital F, and he has a single negative. All right, now this is an imbalance here. To make this work, I'm going to need two fluorines for every barium.

So for every one barium, I'm going to need two fluorines. So the formula for this one will be Ba, a single Ba, and to get two fluorines, I'll put a subscript after it. So it's BaF2, potassium nitride. All right, potassium is K, and the typical charge on potassium is it has a single positive.

We're going to combine that with nitrogen. Symbol is capital N, and the typical charge on this guy is three negatives. All right, now to make this thing work, I'm going to have to have three. potassiums to equal just one nitrogen. And so the formula is going to be K3N.

And there's how we get our 3 to 1 ratio using subscripts. Aluminum chloride. Alright, aluminum is capital A, L, and he's typically 3+. Chloride, we've already done this one, capital C, L, and one negative.

Now to make this work I'm gonna have to have three chlorines. for every one aluminum. So for every one aluminum, I'm going to need three chlorines. So the formula is going to be AlCl3. Barium nitride.

All right, we've been there before. Barium is two pluses. Nitrogen is three minuses.

Okay, now this is weird. Twos and threes. Well, let's think of mathematics and doing some factoring here. Two times three gives you six. So think of this very carefully.

If I take three bariums, now that's three times positive two, that'll give me positive six. And if I take two nitrogens, that's two times negative three, that'll give me negative six. Right, three times two, two times three, they both equal six.

So to make this ionic bond work, I'm going to have to have barium, three of them, and nitrogen. two of them, so the formula is going to come out being Ba3N2, and now their pluses and minuses will equal each other. There is a bit of a problem with some of our metals on the periodic table. Some of them have more than one stable ion, so for example, iron has two.

It can be iron with a two-plus charge or iron with a three-plus charge. Well, how are we going to tell them apart? It's actually pretty easy.

We put a Roman numeral after it, so iron 2 means iron with a two-plus charge, and iron, Roman numeral 3, means iron with a 3 plus charge. So here, for example, in the first row, I've got iron 3 chloride. So what does that mean? Well, it means the cation is iron with the 3 plus.

That's what the Roman numeral 3 means. And, of course, chlorine is Cl, and we know that it has 1 minus. We've seen this before. So to make this work for every 1 iron, I'm going to need 3 chlorine.

So the formula is going to have to be, for every 1 iron, I need three chlorines. It's FeCl3. What about this next one? I've got lead oxide. All right, so it's made up of lead, Pb, and oxygen, O.

Now, lead can come in two different varieties. Sometimes lead can be plus two. Sometimes it can be plus four. Which is it?

Well, to figure that out, we're going to have to have a look at the oxygen. You see, the oxygen is always going to be negative two. There's no getting around that one.

And you'll notice that over here on the formula, I've got two oxygens. And so 2 times negative 2, what I've actually got over here is I've got a total of negative 4, right? Because I have two oxygens in the formula. So if I've got a total of negative 4 charges, what lead must it be? Well, you've probably guessed it.

It's going to have to be the lead with the 4 plus, so that 4 pluses match up with 4 negatives. So this guy is going to be called lead. Which lead?

Lead IV, Roman numeral IV, and then of course comes the oxide, changed into IDE. Nickel III sulfide. Well, nickel is capital N little i, and it's nickel with three positive charges.

Sulfide is a capital letter S, and sulfide has a charge of negative 2. So to make these guys work, here's the twos and threes making six again. So I've got to try and make 6 out of the deal. So for the nickel, I'll multiply that by 2, because 2 times 3 pluses is 6 pluses.

And for the sulfur, I'll multiply this one times 3, because 3 times negative 2 is negative 6. So now my charges match. So you probably see it's pretty easy going from the name to the formula, because the name tells you which metal to use. This next one, we're going to go from the formula to the name. I know I'm going to use copper. and I'm going to use fluorine.

And I've got two of these fluorines, and I know that each fluorine is negative, and I know that I've got two of them here. So what I've got is, I've got a total of two negative charges all together with my fluorine. So what copper is going to match that? Well, according to the formula here, I've got to come up with a charge of two. So I'm going to use the copper two.

I'm going to use the copper two plus, so that my two pluses match my two negatives. And so I'm going to call this fellow copper 2. I'm going to use the 2 plus and fluoride. Now when you spell fluoride, be careful, okay? It's not flower, it's fluoride. So use a U-O-R-I-D-E.

A lot of kids spell it like flower-ide. Chromium 3 sulfide. Now I'm just going to erase some of the... line I made here, so I've got some space to work in.

Chromium 3. Well, the symbol for chromium is capital C, little r, and he's chromium with three pluses. That's this one over here, as opposed to chromium with two pluses. And then sulfide, sulfur is two negatives. Now, here we go again, twos and threes.

So we've got to make six out of the deal. So I'm going to take the chromiums, which is three plus, and I'm going to multiply it by two. That'll give me six.

and I'm going to take the sulfur, which is two negatives, and I'm going to multiply it by three. So it's Cr2S3, and we got that guy worked out. FeO, that's an iron, and that's an oxygen.

But again, which iron? Is it the iron 2 plus or the iron 3 plus? Well, again, look at the oxygen.

The oxygen is two negative. That's all he can be. So I've got to make sure if it's one of each, then this guy must be two positives. So two positives make it.

balance two negatives. So the iron I'm using is the iron I'm using iron oxide. This is how you deal with handling multi-valent metals that have more than one possible charge.

You need to use their partner to figure out what charge they are and the charge is written in the form of a Roman numeral. Last but not least you may have to deal with polyatomic ions. This is a group of non-metals that are clustered together.

They operate as a unit. So polyatomic just means many atoms, and they work together. So for example, here's one, the hydroxide iron, which is OH-, made of one oxygen and one hydrogen, and it always works together as one. They don't separate. They go together as a team.

You can see a list of this on page 44 or on your periodic table in your science data booklet. They can often be recognized by their endings. Look for words that have 8. or ite. So you've already seen ide, I-D-E, that means it's periodic table. If you see ite or ite, you want to look on the chart of polyatomic ions.

Well let's do a few. Barium hydroxide, so the cation is barium, Ba, and hydroxide, well that's an OH. And you can find that on your periodic table if you look at your polyatomic ions. And if you do a little bit of searching and hunting, you should eventually figure out where is that thing. is OH.

There he is. Now an OH typically has one negative charge, but if you recall, barium has two positives when you look him up on the periodic table. So if you're going to make this work, for every one barium, you're going to need two hydroxides.

So here's my barium. Now I need two hydroxides, but they've got to be kept together as a unit. So here's O and H, and then I place brackets around the two of them to keep them together. Then I put my subscript. Now these brackets are incredibly important.

If I don't have that subscript, I'll have BaOH2, and that means all I've got is two hydrogens. But I need two OHs, not just two hydrogens, so the entire polyatomic ion must be bracketed. Iron 3 carbonate. Sorry, that means I'm going to use iron with the 3 plus charge. And carbonate.

Okay, well what the heck is a carbonate? Well here he is down here. Carbonate is C.

CO3 and he's got a charge of negative 2. So I've got plus 3's and negative 2's. I'm going to make 6 out of this deal. So I'm going to take the iron, which is plus 3, and I'm going to multiply that by 2. And I'm going to take the carbonate, which is CO3, and I'm going to multiply that by 3. But I got to do the whole thing. So I put brackets around the entire unit and then I multiply that by 3. And that's how we deal with that.

Copper 1 permanganate. Copper is Cu, and the 1 means it's 1 plus charge. Permanganate. Okay, well, what is a permanganate?

Here it is. He is capital M, little n, there's your manganese, O4, and he has a negative charge. So this is rather interesting.

It looks like one copper will be perfectly balanced by one permanganate. So he's going to be CuMnO4. Put them all together.

We don't need any brackets because it's one of each. Everything's just fine. Now here I have the formula. I've got gold, AU, and I've got nitrate, which is NO3.

Now it says I've got three nitrates, so that's kind of curious. Why is that? Well, if I look up my nitrate on the chart of polyatomic ions here, where is my nitrate?

Here we go. I kind of cut it off here. Nitrate is NO3 and it has a charge of negative 1. And it's saying over here that I've got three of them.

So if I've got three of these negative 1s, then the gold must be three positives. All right, so three positives will balance three negatives. And so what have I got here? I've got gold, three, and I've got, now watch the spelling, NO3 is nitrite, I-T-E. Nitrate is NO4.

Here's one that's made of two polyatomic ions, this one here and this one here. NH4 is known as ammonium. I don't know if I'm going to get it all in here. and P04 is known as phosphate. So what I've got here if I put them together, I've got ammonium phosphate.

And we need three ammoniums to go with that phosphate. Reason why is because ammonium only has a charge of a single positive, just one positive, but a phosphate is worth three negatives. That's why I need three ammoniums to work with that one. Here's an interesting one. I've got K.

Now, I know what that is. That's potassium. And then I've got Cr2O7.

Well, that guy's called dichromate, and he typically has a charge of negative 2. So Cr2O7. This whole thing is worth negative 2. Potassium, if you recall, is worth a positive 1. That's why I've got to have two potassiums to match that dichromate. I need two of them to equal the negative two charges on the dichromate.

And so what's this fellow going to be called? He's going to be simply called potassium dichromate. And so this will hopefully help you realize that when you've got a polyatomic ion, use this little chart that's on your periodic table and let that help you find the names of these fellows.

Transcript for:Understanding Ionic Compound Naming

Transcript for:
Understanding Ionic Compound Naming