Naming Compounds – Part 2


Mr. Andersen shows you how write the chemical formula for chemical names.

Transcript Provided by YouTube:

00:04
Alright. Let’s clear that off and go to the next one. And let’s just write
00:09
covalent formulas. And so once you’ve gone through and figured out how to go from the
00:14
formula to the name, going from the name from the formula is really easy. And so let’s start
00:19
with this first one. This is dihydrogen monoxide. And so what’s first? We have 2 hydrogens.
00:26
So I’m going to write H2. And then we have one oxygen. So that would be H2O. And so instead
00:33
of saying water, you can ask people if they could pass you a glass of dihydrogen monoxide.
00:38
And they’ll tell you that you’re a total geek. Let’s go to the next one. Dinitrogen trisulfide.
00:43
That’s going to be N2. And then we have S3. Because we have 3 of these sulfides. Let’s
00:51
got to the next one. Silicon dihydride. That’s going to be Si. And then we’re going to have
00:57
H2. Or if we go down here, sulfur hexafluoride. That’s just going to be SF6. And so covalent,
01:08
writing the formula is really easy when we’re going from the name to the actual formula.
01:12
Okay. Let’s go to the last one. And that’s writing ionic formulas. Ionic formulas remember
01:18
are always written where you have the cation on this side and the anion on this side. So
01:23
let’s go back. We’ve got lithium and oxide. Now when you’re going from the name to the
01:29
actual formula of it, as far as ionic formulas go, it’s a little more complex. Because you
01:34
have to make sure that it balances. And so we’ve got a lithium on this side and an oxide
01:39
on that side. We want to go find that on here. So lithium has a plus 1 charge. Oxide has
01:48
a 2 minus charge. And so when I write that out I have to balance that. And so this is
01:53
going to be Li. So lithium had a one charge. So I’m going to have to put 2 of those with
02:01
one oxygen. In other words I need to balance it out. Let’s go to the next one. We’ve got
02:05
iron chloride. We know that iron has a 3 plus charge because this is iron (III). So we better
02:11
figure out what the charge of chloride is. So let’s look back at our periodic table.
02:16
Chloride is going to be way over here. It has a minus 1 charge. So let’s go to that.
02:20
So we’ve got a minus 1 charge on this side. And so we have to balance that out. So we
02:25
know it’s going to be Fe. We don’t write the Roman numeral. Because we only write that
02:28
in the name. And so how many of the chlorine atoms or chloride ions do we have to have?
02:34
It’s going to be FeCl3, if you were thinking that. Let’s go to the next one. Manganese
02:39
(IV) chromate. So that’s going to have a 4 plus charge on the left side. And now we’ve
02:44
got to figure out what chromate actually is. And so let’s go to the periodic table. So
02:49
chromate is going to be, let me find it on here. Chromate is going to be way up here.
02:55
So chromate is going to be CrO4. And that’s 2 minus. So CrO4 and that’s going to have
03:04
a 2 minus charge. And so let’s go forward for a second. So this is right here going
03:09
to have a 2 minus charge on this side. And so how many of those do we have to have? Well
03:13
we’re going to have two of the chromates. And so let’s write manganese first. So that
03:18
going to be Mn. And now all of this whole polyatomic anion has a 2 minus charge. And
03:25
this is where the parenthesis come in handy. So I’m going to put a parenthesis around CrO4.
03:31
So this is CrO4 like that. And I have to have 2 of those to balance the charges. So I’m
03:38
going to put a two right down here. And so that’s what that subscript outside the parenthesis
03:42
actually means. Let’s go to the last one. Zinc. So if we find zinc on our periodic table,
03:48
zinc is going to be, it’s way over here. So zinc has a 2 plus charge. And we’re going
03:56
to combine that zinc with thiocyanate. And so this has a 2 plus charge. And now let’s
04:02
find the thiocyanate. Thiocyanate is going to be way over here and that is SCN. And that
04:11
has a 1 minus charge. So let me go forward and figure out this last one. So this has
04:17
a 1 minus charge on this side. And so what I’m going to write for this, this is going
04:21
to be zinc. And so that is going to be, let me go back for a second, it’s going to be
04:26
zinc which has a 2 plus charge. And then I’m going to put my thiocyanate, but I’m going
04:31
to have to have two of those because they have a 1 minus. So I’m going to put a SCN
04:34
and then I’m going to have to have two of those to balance out. So now we’ve gone from
04:41
writing the name to writing the formula. Now why do we have to balance all of these out?
04:45
As I clear this, remember all of the atoms on here want to be a noble gas. In other words
04:53
the noble gases have full outer valance shells. And so if you think of it like a tennis ball,
04:59
a tennis ball, if it had electrons around the outside of it, if you don’t have eight
05:04
you’re a very unstable tennis ball. And if we can either lose electrons and become a
05:09
cation we can become stable. Or we can gain one to get an outer shell that’s stable, then
05:15
it’s a happy atom. And so hydrogen has one electron. It would love to get two. And it
05:19
can share that with oxygen. That’s why water ends up being H2O. And so that’s how you name
05:24
things. Hopefully you can look at a can of Mountain Dew now and you can figure out what’s
05:28
actually on it. And so I hope that was helpful.


This post was previously published on YouTube.

Photo credit: Screenshot from video.