How to Name Chemicals Made Easy

"How to Name Chemicals, Made Easy,"
brought to you by Ketzbook.

Welcome back and thanks to all my
subscribers and patrons out there

for making this video possible.

In this video, we're going to learn
how to name binary compounds.

A binary compound is a chemical
that is made of two different elements,

so naming binary compounds is really the first
step in learning how to name ANY chemical.

This video will cover how to name
simple ionic compounds,

multivalent ionic compounds,
and simple covalent compounds.

However, it will not cover
polyatomic ions or organic compounds.

I will cover those topics in subsequent videos.

Let's start out by looking
at two common examples:

CaCl2, which is calcium chloride,
and CO2, which is carbon dioxide.

In these examples and in general,

the MORE metallic or LESS electro-
negative element is written first,

and the LESS metallic or MORE electro-
negative element is written second.

This is true for both the chemical name
AND the chemical formula.

You can determine the metallic nature of
an element by looking at the periodic table.

In THIS periodic table, metals are red,
nonmetals are blue, and metalloids are purple.

As you move toward the metals --
that is, as you move down and to the left --

the elements become more metallic.

In the case of calcium chloride,

calcium is a metal and
chlorine is a nonmetal,

so calcium is written first.

However, in the case of carbon dioxide,
both carbon AND oxygen are nonmetals,

but because carbon is to the left of oxygen,
it is more metallic than oxygen.

Remember, as you move down and to the left,

elements become more metallic,

so carbon is written first and then oxygen.

There are a few other things that
we should learn from our examples.

First of all, the first element's
name remains UNchanged,

while the ending of the second
element changes to "-ide."

This is true for both ionic
and covalent compounds.

We can see that calcium
and carbon are the same,

but chlorine changed into chloride
and oxygen changed into oxide.

Also, we notice that there is
a "di-" prefix in front of oxide,

which corresponds to the 2 in CO2.

However, calcium chloride,
which also has a 2 in the formula,

does NOT have a di- prefix. Why is that?

Because calcium chloride is ionic
and carbon dioxide is covalent.

Ionic and covalent compounds
are named differently,

so the first thing you need
to do in naming compounds

is to figure out whether the
compound is ionic or covalent.

Ionic compounds are typically
made of a metal and a nonmetal,

just like calcium chloride;

while covalent compounds are composed
of only nonmetals or metalloids,

just like carbon dioxide.

Ionic compounds do NOT use prefixes,

but covalent compounds DO use prefixes
to indicate the numbers in the formula.

Let's focus on covalent compounds for a minute.

The most common prefixes for
covalent compounds are written here.

If they are unfamiliar to you,
you should memorize them.

Before we look at any more examples,

we should notice that the "mono-" prefix
for 1 is not used for the first element.

CO2 is NOT "monocarbon dioxide,"
but simply "carbon dioxide."

In the same way, BF3 is boron trifluoride.

The mono- prefix is not used
for the first element,

However, mono- IS used for the second element.

For example, N2O is dinitrogen monoxide.

In that case, there IS a
prefix for both elements.

Notice also that the mono- lost its last "o."

It is NOT "dinitrogen monooxide."

In general, an "a" or "o"
at the end of a prefix

will be dropped if followed by oxygen.

So P2O4 is diphosphorus tetroxide,

NOT "diphosphorus tetraoxide,"
because the "a" is dropped.

Let's try a couple more.
How would you name a B2S3?

Yes, diboron trisulfide.

And what is the formula
of arsenic pentachloride?

That's right, AsCl5.

As long as you know the prefixes,
you can name any binary covalent compound.

But what about ionic compounds?

Remember that CaCl2 is simply calcium chloride.

In general, ionic compounds
do NOT use prefixes.

That means that Li3N is simply lithium nitride

and Al2S3 is simply aluminum sulfide.

But how can you figure out the formula
from the name without prefixes?

We can use the octet rule.

The octet rule basically states that main group
elements tend to gain or lose electrons

in order to have the same number of
electrons as the nearest noble gas,

which is typically 8 valence electrons.

So when forming ionic compounds,

elements with 1, 2, or 3 valence electrons
will LOSE all their valence electrons,

giving elements in column 1 a positive 1 charge;
elements in column 2 a positive 2 charge;

and then skipping the transition elements,
aluminum forms ions with a positive 3 charge.

Carbon has 4 valence electrons and
generally does NOT form single-atom ions,

so we will skip the carbon column.

Nitrogen has 5 valence electrons,

so it'll gain 3 electrons and become
like neon and have 8 valence electrons.

Because electrons are negatively charged,

those 3 electrons will give
nitrogen a negative 3 charge.

Similarly, oxide has a negative 2 charge
and fluoride has a negative 1 charge.

In general, all elements within a column

will form the same charge ions unless
you cross the metalloid staircase.

Let's try some examples.

What is the formula of magnesium fluoride?

Magnesium in column 2
typically forms positive 2 ions,

and when you write the formula of the ion,
it should be Mg 2 plus, not Mg plus 2.

Fluoride is in the next to last column,
so it should have a negative 1 charge,

which we write simply as F minus,
NOT as F minus 1 or F 1 minus.

So how do the charges lead us to the formula?

Well, all compounds need to be neutral,

so we need to balance the charges of the ions.

In this case, magnesium has a positive 2 charge,

but fluoride is only negative 1,

so we need two fluorides
for every one magnesium

in order to have an overall charge of 0.

That means that the formula
of magnesium fluoride is MgF2.

No subscript after Mg means that there's
only one magnesium in the formula,

and the 2 after the F means that
there are two fluorides in the formula.

Now let's pause and think about

HOW the formula of the compound
is related to the CHARGES of the ions.

Notice how the 2 charge of magnesium
becomes the subscript of fluorine,

and notice how the 1 charge of fluoride
becomes the implied 1 subscript of magnesium.

This is a general principle.

The magnitude of one ion's charge
becomes the subscript of the other element.

Let's try a couple examples.

What is the formula of aluminum oxide?

Aluminum ions have a positive 3 charge
and oxide ions have a negative 2 charge.

That means the formula
of aluminum oxide is Al2...

(the 2 comes from the oxide's charge)

...O3, and 3 comes from aluminum's charge.

Let's try one more.

What is the formula of calcium sulfide?

Calcium ions have a positive 2 charge

and sulfide (just like oxide)
has a negative 2 charge.

That means the formula of calcium sulfide
SHOULD be Ca2S2;

however, keep in mind that those subscripts
tell you the ratio of the ions,

so this formula means that calcium
and sulfur are in a 2-to-2 (2:2) ratio.

A 2:2 ratio, of course, is the same
as a 1:1 ratio,

and for ionic compounds
and ONLY ionic compounds,

we should reduce the ratio
to the smallest whole numbers.

So the formula of
calcium sulfide is simply CaS.

Okay, we're almost done with
how to name binary compounds,

but what about all those metals
in the middle of the periodic table?

It turns out that they
do NOT follow the octet rule,

and most of them can form
more than one different stable ion.

Therefore, we will call them multivalent ions.

For example, iron can form
positive 2 OR positive 3 ions.

When combined with chloride, for example,

the iron 2 ions make FeCl2
and the iron 3 ions make FeCl3.

So what do you call those compounds?
They cannot BOTH be called iron chloride.

You might be tempted to name them
with covalent prefixes, like iron dichloride,

but that would be WRONG.

Instead, multivalent ionic compounds are named

using Roman numerals
for the charge of the metal,

so FeCl2 is called iron(II) chloride
and FeCl3 is called iron(III) chloride.

Remember that the Roman numerals indicate
the positive charge of the metal ion,

NOT any number in the formula.

Just in case you're not familiar
with Roman numerals,

here's a list for the ones you
need for naming chemicals.

Let's try a few examples.

What is the formula of copper I phosphide?

First, we write down the ions.

From its name, we know that copper I
has a positive 1 charge, so that's Cu plus.

Phosphorus has 5 valence electrons,

so it will gain 3 electrons to make
phosphide, which is P3 minus.

Next, we can just switch the 3 and the 1,
so the formula is Cu3P.

Going from the formula
to the name is a little harder.

What is the name of CrBr3?

Because we don't know the charge
of chromium in this compound,

it is important to first calculate the
total negative charge of the anions.

Bromine is a halogen in the
next-to-last column of the periodic table,

so bromide has a negative 1 charge.

The "3" after Br means that there are
3 bromides in the formula,

so the total charge of
the anions is negative 3.

That means that the total charge
of the cations must be POSITIVE 3

in order to balance the charge.

Since there is only one chromium in the formula,

its charge is positive 3.

That means that the name of CrBr3
is chromium(III) bromide.

Remember that the Roman numeral 3 (III)
refers to the charge of chromium,

NOT the number of bromides in the formula.

Now, anytime you learn something new,

you really need to practice it
to make it your own,

so I'm going to give you three chemicals
and I want you to try to name them.

I also want you to determine the formula
of a binary compound of iodine and barium.

I'll even give you the periodic table
to help you out.

Please pause the video now

and solve these problems using
everything you learned in this video.

[PAUSE]

Alright, now for the answers.

Before you begin, you first need to determine
what type of compound each one is.

The first compound is an
alkaline metal and a nonmetal,

so it is a simple ionic compound
that obeys the octet rule.

Keep in mind that the metals
which OBEY the octet rule

are primarily the ones in the
first two columns and aluminum.

Nearly all the other metals are multivalent.

Since Li3N is a simple ionic compound
that obeys the octet rule,

it should NOT have any
prefixes or Roman numerals.

Its name is simply lithium nitride.

The second compound is composed of
two nonmetals, so it's a covalent compound.

That means its name
uses prefixes for subscripts,

so its name is carbon tetrachloride.

Remember that the mono- prefix
is NOT used for the first element.

The third compound is a
transition metal and a nonmetal,

so it is a multivalent ionic compound.

In order to figure out
the charge of the manganese,

we need to calculate the total charge of the anions.

Oxygen, with 6 valence electrons,
gains 2 electrons to form O2 minus,

and there are two oxides in the formula.

Remember the subscript 2 in MnO2

means there are two oxides
for every one manganese.

If we add up the charges of the anions,

we get negative 2 plus
negative 2 equals negative 4,

and to balance that, the cations
must have a POSITIVE 4 charge.

Since there is only one manganese,
its charge must be positive 4;

therefore, its name is manganese 4 oxide.

The last compound is a nonmetal
and an alkaline earth metal,

so it's another simple ionic compound.

Iodide, like all halides,
has a negative 1 charge;

and barium in the second column
has a positive 2 charge.

You may, at first, think that the formula
would be I2Ba, but that is INCORRECT

because the cation or the more metallic
element should be written first,

so the formula is BaI2 and the name
of the compound is barium iodide.

Thanks so much for watching the entire video.

If you found it helpful, please like, subscribe,
or check me out at ketzbook.com

If you have any questions or comments,

be sure to share them below
and have a wonderful day. [END]