# Naming Compounds – Part 2

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

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#### 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.

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This post was previously published on YouTube.

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Photo credit: Screenshot from video.