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Mr. Andersen shows you how to name covalent and ionic compounds.
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Transcript Provided by YouTube:
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Hi. It’s Mr. Andersen and today I’m going to show you how to name chemical
00:10
compounds. And the reason we do that is when you’re you should be able to pick up anything
00:15
and figure out what’s actually in it. And so if we’ve got a can of Mountain Dew, this
00:18
is old school Mountain Dew, and we look at what’s inside it, there’s going to be water
00:22
and sugar. And we know what those things are. But there’s also going to be, for example,
00:26
sodium benzoate. And at the end you’ll actually know what that is. Or calcium disodium. You
00:31
should be able to figure that out when were done. What that actually is. And so let’s
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get started. First of all let’s start with the rule of thumb. The rule of thumb says
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that if you hold your thumb up to the periodic table things on one side of your thumb are
00:45
going to be non metals. And so if I hold it up like this, everything on this side of my
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thumb is going to be a non metal. Everything on this side of my thumb is going to be a
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metal. And so there are really just three types of bonds. If you have two metals together
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we call that a metallic bond. If you had two non metals together we call that a covalent
01:05
bond. And then if you have one metal and one non metal together we call that an ionic bond.
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And if you don’t know how to figure out what kind of a bond it is, you want to look back
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to the previous podcast where I talked about what exactly that is. One quick way to do
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it is to just look at the differences in the electronegativities. So calcium is one. If
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we look over here for example, nitrogen, that’s 3.04, so I should be able to tell right away
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that that’s going to be an ionic bond, just from the electronegativities. Okay. Let’s
01:34
start with the easiest one. And that is naming covalent compounds. First of all you have
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to figure out how do I know which of the two atoms comes first. In other words why is it
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carbon dioxide and not dioxygen mono carbon, excuse me, carbide. So let’s look on the periodic
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table and I’ll talk about rule one and rule two. Rule one says you always start with the
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lower group number. And so why is it H2O? It’s because hydrogen has a lower group number
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than oxygen, which is over here. And so hydrogen gets to go first. Now you might immediately,
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if you’re smart be thinking, well, okay that works. We’re always going to go kind of from
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left to right. But what if they’re in the same column? And so sulfur dioxide is an example
02:18
of that. We’ve got sulfur here and we’ve got oxygen right above it. So who goes first?
02:23
Well you’re always going to start with the one that has a greater period number. And
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remember period numbers are going to increase as we go down the periodic table. And so sulfur
02:31
goes before oxygen just because it’s lower on the periodic table. So once we figure out
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who goes first, then it’s really easy to figure out the names of these. So let’s start with
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carbon dioxide. Carbon dioxide, carbon is going to go first. Whenever you’re naming
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covalent compounds, you’re just going to put the name of the atom first and then you’re
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going to put the anions second. These little subscripts tell you how many of those ions
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you actually have. One more thing, so first of all we put the atom first and then we put
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the second as an ion, or in this case it’s a negative ion called and anion. And then
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we’re just going to use this chart over here to figure out how many of them we have. It
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goes from mono meaning one all the way up to deca meaning ten. We rarely use these ones
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down here. But you might as well learn these first four because we use those quite a bit.
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So let’s start with carbon dioxide. Now you might want to say well there’s only one carbon
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and so let’s call that mono carbon. But you can see here that you don’t put a mono on
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the first one. Also if we have like mono oxide, that sounds kind of silly. You just kind of
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lump that together and that would be monoxide. So let’s start with the first one. So we’ve
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got carbon first. So we’re just going to write the name of that element. So carbon is first.
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And then we have two of the oxygens. And so that’s going to be dioxide. And you’ve heard
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that before. Carbon dioxide. Let’s look at the next one then. What’s the first element?
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The element is going to be, P is going to be phosphorus. And then we have N next. Now
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it’s not nitrogen. It’s going to be the ion of nitrogen. So let’s kind of skip forward
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and see what that is. It’s way up here. Let me get in a color you can see. It’s going
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to be nitride. And so if you’re ever trying to figure out what the ions are, you can look
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on our, we use the in class, Periodic Table of Ions. And it’s going to tell what the name
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of that is. So let’s go back and finish this one out. So this one, we have phosphorus,
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but we have three of those. And so this one is going to be triphosphorus. And then we’ve
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got four of these nitrides. So that’s going to be tetranitride. So that’s the name of
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P3N4. If you go to the next on this is carbon, so we’re just going to write the name first.
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Carbon. And then we’ve got four of these hydrides. And so that’s going to be carbon tetrahydride.
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So if you look at this again, we’re always writing the atom name first and then we’re
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always going to write this, instead of tetrahydrogen it’s going to be hydride. We’re going to write
05:08
that anion for that. So that’s naming covalent compounds Let me erase that and let’s go to
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ionic compounds. Ionic compounds, it’s actually easier. There’s just two rules. Rule number
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one, you’re always going to write the cation first and the anion second. So you’re always
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going to write the positive charge first and the negative charge second. And the only other
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tweak on that is that there are some elements, let’s kind of skip back for a second. So if
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you look way over here. Let’s look at for example iron. Iron, you can write iron in
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a number of different ways. We can have iron III. We can have iron II. Some of these will
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have multiple states that they can have. And so if there ever could be more than one type,
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like iron III or iron II, in Roman numerals we’re going to note which one of those are,
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which one they are. And so let’s take a look at one of these and actually do that. So let’s
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look at the first one. So this lithium and oxygen. And so all we do is look on our chart
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and we figure out what the name of those ions are. So if we go back and here, here’s lithium
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all the way over here. So lithium is going to be the name of the cation. And then we
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go over here and we find the anion. And it’s just simply lithium oxide. And so this one
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would lithium oxide. Now if you look at it, why is it written as Li2O? Because lithium
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has a positive charge and oxygen or the oxide anion is going to have a 2 minus charge, so
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we have to have 2 of the positive charges to balance that out. Now let’s look at the
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next one. This one looks a little bit scary. What this one, you shouldn’t be scared though.
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If we ever see something that is written in parenthesis, that means that it’s a polyatomic
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ion. That means it’s an ion. It still has a charge, but it’s made up of more than one
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atom. In this case we have NH4. So let’s just go back to our chart and find out where that
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is. I’m going to look around here until I find it. So it’s way over here. So this would
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be NH4. And that stands for ammonia. And so that’s going to be ammonia. And now let’s
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look back at what we had. And now we have a P. And so that’s the other part. That’s
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going to be our anion. So let’s find that. That’s going to be phosphide over here. So
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if we look at ammonia there’s only one type it can be. NH4 and phosphide is going to be
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P. And so let’s just kind of go forward and write that as it is. So that is ammonium phosphide.
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So again, pretty easy. We’re just writing the cation first and then the anion second.
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Now let’s look at this one. We’ve got copper. And then it looks like we have another one
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of those polyatomic ions. In this case it’s going to be an anion. So let’s go find it
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on the chart. First of all we have to find copper. And so copper, I’ve kind of written
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all over it, but copper is going to be, where’s copper going to be? Copper is going to be
07:57
right here. And so copper can have two states. Copper can either be Cu2+ or it could also
08:05
be CU1+ or just plus. And so we have to figure out which one it’s going to be. So let’s go
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take a look at that. So here we’ve got copper. And now we’ve got this. We’ve got to figure
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out what that NO3 is. So let’s go back again. So where is NO3. NO3 is going to be written
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on our chart. Looks like I’m going to have to erase some of this stuff. So if we look
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up here, NO3 on our chart is going to be, NO3 is going to be nitrate. And so nitrate
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is going to be right here. It’s NO3. And it has a 1 minus charge. And so now we’ve got
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our copper which we know could be copper II or copper I. And now we know that nitrate
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has a minus 1 charge. So let’s try and figure out what this is. So nitrate has a minus 1
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charge. So this is minus 1 for this nitrate right here. But we don’t just have one of
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them. We actually have two of those. That’s what this subscript means down here. And so
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on the right side of this we have two of these minus 1 charges. And so we have a 2 minus
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charge on the right side. If you look on the left side, well, what copper do we have? Well
09:12
we know right away that since there’s 2 minus charge on this side we actually have copper
09:16
II. So let’s write that out. It’s going to be copper. Now we know it’s going to be copper
09:22
II. So in Roman numerals in there I’m going to put copper (II). That’s going to be nitrate.
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So again the only time we have to write those Roman numerals is if it could exist in two
09:33
different states. Let’s go to the next one. Looks like we’ve got nickel here. And then
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we have SO3. So figure out what SO3 is. Let’s go back. So let’s find SO3 on here. SO3 is
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actually going to be sulfite. And it has a 2 minus charge. Now if we find nickel, nickel
09:51
can either be nickel II or it can be nickel III. So again we have sulfite and we’ve got
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nickel. And you got to kind of switch between these. So now we’ve got nickel and we’ve got
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sulfite. Sulfite remember had, sulfite had a let me go check again, had a 2 minus charge.
10:08
And so this has a 2 minus charge on this side. And we have 3 of those. And so what do we
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have net on the right side? We actually have a 6 minus charge on the right side. And so
10:19
what nickel do we have? Well if look on the left side we have 2 of these. And so to balance
10:25
out that 6 minus charge on the right, it has to be nickel (III). And then on the right
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side that’s going to be sulfite. Let me add some dots here. And so we know that it’s balanced
10:43
on either side and so we’re going to call that nickel III sulfite.
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This post was previously published on YouTube.
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Photo credit: Screenshot from video.