name

Naming Covalent Molecular Compounds



Sharing buttons:

let's look at how to write names for

compounds like these that are made of

two nonmetals the nonmetals are the

elements to the right of the staircase

on the periodic table now

compounds like these that are made of a

nonmetal and another nonmetal two

nonmetals are called covalent or

molecular compounds and that's because

the elements that are in them are held

together by covalent bonds and they're

held together in groups called molecules

now the way we name covalent or

molecular compounds is different from

how we name ionic compounds ionic

compounds contain a metal and a nonmetal

the metals are the elements here on the

periodic table and I've written in some

of the most common some examples of

ionic compounds and of how we name them

are things like calcium fluoride and

iron ii oxide so if you have to name a

compound the first thing you want to do

is figure out what type of elements are

in it if the compound is made of a metal

and a nonmetal it's an ionic compound I

have a whole bunch of videos on how to

name I on a compounds and how to write

formulas for them if you need to name a

compound that's made of a nonmetal and

another nonmetal well that's a covalent

or molecular compound and naming these

is what this video is going to focus on

okay here's our first chemical formula n

2o 3 it's made of two nonmetals we're

going to write a name for it following

these steps so here's the first one says

for the first element start with the

element name what I'm talking about the

first element I'm talking about the

order that these elements are in in this

chemical formula so the first element

here is nitrogen n so it says start with

the element name okay so I'm going to

put nitrogen down that's the element

name here now for the second element so

that's this here oxygen for the second

element start with the IDE name now the

IDE name is the version of the element

name that ends in IDE these are actually

the same names that we use to name

negative ions so we've got oxygen here

we're going to use its IDE name which is

oxide

okay so we got nitrogen and we got oxide

now use prefixes to show how many atoms

of each type there are the prefixes

here's a list of them are like these

little tags that we put on the front of

each name to tell us how many atoms of

each type we have so n 2 we got two

nitrogens which means that we want to

use this prefix for to die so put that

in front of the element name dinitrogen

now o 3 which means that we have three

oxygens so i'm going to use the prefix

tri here and write that in front of

oxide and so the name for this compound

is dinitrogen trioxide we put the

element name here we put the IBE name

here and then we use the prefixes to

indicate how many atoms of each type we

have let's look at a few more examples P

for s 10 okay for the first element

we'll start with the element name P is

phosphors if you didn't know that you

could look it up on the periodic table

for the second element that's s here

start with a IDE name so s is sulfur and

it's IDE name is sulfide okay so those

are the two names now we're going to use

prefixes to show how many atoms of each

type we have we got P four so that means

we have four phosphorus atoms so four is

tetra we use the tetra prefix tetra and

then four sulfide we got ten so we'll

use this prefix deca deca so the name of

this compound is tetra phosphorus deca

sulfide let's move on we're going to add

a couple more steps to deal with more

complex formulas here's the next step

that we're going to talk about do not

use mono on the first element I'm going

to show you what this means by working

through

naming this formula we'll start it off

just normally so for the first element

start with the element name that's

carbon and then the second element which

is fluorine we use the IE de name which

in this case is fluoride okay now we get

to the prefixed part and this is where

things change a little bit so it says do

not use mono on the first element carbon

here we only have one of them so you

might want to use mono and put it in

front of here that would be a perfectly

logical thing to do but for whatever

reason we don't use mono on the first

element if there's just one of them we

just leave it like this you don't put

anything there so we have one carbon

we're just going to call it carbon and

then for fluorine here in front of

fluoride I'll put the prefix just like I

would any other time so I have four of

these fluorines so i'm going to call it

tetra tetrafluoride so carbon

tetrafluoride not mono carbon

tetrafluoride just carbon tetrafluoride

is how we name this because if you got

just one of the first element you don't

use anything pcl5

let's name this so p the first element

is phosphorus CL the second element is

chlorine and chlorines IDE name is

chloride so there it is now we get to

the prefixes phosphorus here we only

have one of them so we're not going to

use mono here we're just going to keep

it as phosphorus and chlorine we have

five of those so we're going to use ten

two here as the prefix so it's going to

be Penta Penta chloride and phosphorus

pentachloride not mono phosphorus

pentachloride just phosphorus

pentachloride is how we name this now

there's one more step that we're going

to add I'm going to talk about that next

okay there's one more step to keep in

mind and I'm going to show it to you as

I work through this example

okay CL 2 o so the first element here CL

is chlorine and oh here is oxygen its

IDE name is oxide okay so now the next

thing I'm going to do is I'm going to

use these prefixes

so I got two chlorines so I'm going to

use dye dye for two up here and then

oxide I got seven of those so I'm going

to use the prefix hepta now try saying

this compound name

we got dichlorine heptoxide hear that

hep dioxide thing is kind of awkward to

pronounce so to prevent us coming up

with these really weird names there's

one more rule and that's that if you

have a o or o o turn it into oh here's

that means we got this heptoxide here so

to make this easier to pronounce we turn

the a o that we see right there into

just an O so I'm going to get rid of

that a going to get rid of that a and

I'm going to turn this compound name

into chlorine heptoxide so not heptoxide

but just heptoxide so you get rid of

that a if it's next to an O there let's

do one more P 406 so the P phosphorus is

our first element and then oh we got

oxide that is a ID name for oxygen here

all right now let's use the prefixes

switch to our prefix table here we have

four phosphorus so we're going to use

the tetra prefix so tetra tetra

phosphorus and then for oxygen we have

six of those so we're going to use hexa

here and just as before we end up with

this awkward name hex oxide we get an AO

so we're going to get rid of this a-here

soup I always like knock that name out

of the way hexa oxide and that turns it

into tetra phosphorus hex oxide you know

I forgot to circle the name and the last

one and this is just so satisfying so I

did it really slowly to make up for the

fact I didn't circle the last one so we

get rid of this we get rid of this

a-here tetra phosphorus hex oxide so I

wanted to

one more example that pulls in examples

of all of this it's like a good review

for all of these things here's our last

formula this is a really good review

it's just C O so the first element is

carbon

the second element is oxygen its ite

name is oxide ok so now for the prefixes

carbon we've only got one of them so

remember don't put anything in front of

it we just call it carbon but we have

one oh and if you have one of the second

element you do use a prefix so we use

the mono prefix here so mono now mono

oxide gives us the same kind of weird

pronunciation thing it gives us an oo

here so we're going to get rid of this

oh I'm going to try to not knock this

name out here oh just a little bit

really good and we call this we change

the name from mono oxide to carbon

monoxide which is probably something

that you've heard of before here's just

some quick information about how we

change these prefixes to avoid an

awkward pronounciation problem we only

really have this problem with oxide

because it begins in O and so we get rid

of the O here in mono and we get

monoxide then we don't have to worry

about dire try because they don't end in

aro and then for all of these others 4

through 10 we get rid of all of these

A's so we get tetroxide pentoxide hex

oxide heptoxide oxide non oxide and Dec

oxide so here's how we name covalent or

molecular compounds with two nonmetals

just follow each of these steps one

thing to keep in mind this mono for the

first element really confuses a lot of

people so remember not to use mono if

there's just one of the first element

keep this in mind try to prevent

yourself from writing names that have

really awkward pronunciations with a o

or o Oh turn it into o keep these things

in mind you should be all set