Chemistry Lecture 3C
Names and Formulas of
Chemical Compounds
(Inorganic)
Formula to Name
First, you must ask yourself if the given
compound is inorganic.

It is an inorganic compound if it does not
contain carbon (except when bonded to a
metal). The exceptions to this are C, CO,
and CO2.
Secondly, you must determine the type
of bond that is in the given compound.
Formula to Name: Ionic
If the compound contains an ionic bond, first
look at the metal.
Does the metal have more than one
oxidation state?

This can be found by looking at your periodic
table in the box labeled oxidation for the metal at
which you are looking.
If no, then write the name of the metal as it
appears on the periodic table.

For example: Na is sodium
Formula to Name: Ionic
If the metal has more than one oxidation
state, you must determine its charge in the
given compound.




For example: Cu2O
Oxygen always has a charge of –2 in ionic
compounds, so each copper must have a charge
of +1 for this compound to have an overall charge
of zero.
Then write the name of the metal as it appears on
the periodic table followed by its charge in Roman
Numerals
Cu2O is copper (I)
Formula to Name: Ionic
Is there more than one type of nonmetal in the given compound?
If no, then write the name of the nonmetal as given on the periodic table but
change the ending of its name to –ide.

Examples:
 Phosphorus becomes phosphide
 Oxygen becomes oxide
 Chlorine becomes chloride
Formula to Name: Ionic
If there is more than one type of nonmetal, then you have a polyatomic ion.

A partial list of these can be located on
your periodic table.
 Examples: SO4 is sulfate, CO3 is carbonate,
OH is hydroxide, etc.
Once you find it on your periodic table,
you simply write the name as given
following the name of the metal.
Formula to Name: Ionic
Let’s try some out!
NaCl

sodium chloride
PbS2

lead (IV) sulfide
MgOH

magnesium hydroxide
Formula to Name: Ionic
Questions?
Name to Formula: Ionic
Ionic compounds should be easy to
recognize by their names as they should
include the name of a metal followed by
that of a non-metal or polyatomic ion.
Examples:



copper (II) sulfide
sodium hydroxide
calcium phosphide
Name to Formula: Ionic
First determine the symbol for and oxidation
state of the metal named.
Examples:




sodium hydroxide: Na1+
calcium phosphide: Ca2+
copper (II) sulfide: Cu2+
Remember, if there is more than one possible
oxidation state for the given metal, then look to
the Roman Numeral following its name in the
given formula to find its charge in the given
compound.
Name to Formula: Ionic
Once you know the symbol and charge
of the metal in the given compound,
look at the rest of the name.
If the ending of the formula name is –
ide, then it is probably a single nonmetal.

The exception to this is hydroxide which is
a polyatomic ion.
Name to Formula: Ionic
Once you determine if it is a single
non-metal you are looking for or a
polyatomic ion, you must determine its
symbol and charge.
Examples:



sodium hydroxide: OH1calcium phosphide: P3copper (II) sulfide: S2-
Name to Formula: Ionic
Now that you know the symbols for
and charges of the elements involved in
the given compound, you can balance
the charges.
The correct formula for an ionic
compound is that which contains the
least amount of atoms necessary to
make the overall charge of the
compound zero.
Name to Formula: Ionic
Let’s balance the charges for our
examples!
Examples:
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copper (II) sulfide: Cu2+ S2CuS  the charges are equal and opposite
calcium phosphide: Ca2+ P3Ca3P2  3 Ca = +6, 2 P = -6
sodium hydroxide: Na1+ OH1NaOH  the charges are equal and
opposite
Name to Formula: Ionic
Let’s try some more!
magnesium sulfate

MgSO4
chromium (III) chloride

CrCl3
manganese (II) nitride

Mn3N2
Name to Formula: Ionic
Questions?
Formula to Name:
Covalent
If it is an inorganic compound, but
contains a covalent bond instead of an
ionic bond, then the process to name it
is slightly different.
The main difference is that you will be
using prefixes to identify the quantity of
each element in the compound.
Formula to Name:
Covalent
Prefix
# of atoms
Prefix
# of atoms
mono-
1
hexa-
6
di-
2
hepta-
7
tri-
3
octa-
8
tetra-
4
nona-
9
penta-
5
deca-
10
Formula to Name:
Covalent
Determine the name of the element
belonging to the leftmost symbol in the
compound.
Look to the right of the symbol and see
if there is a small number.


If there is no number, then there is only
one atom of that element.
If there is a number, it denotes how many
of that element is in the compound.
Formula to Name:
Covalent
Once you determine how many atoms of the
element there are and the element’s name,
you can write the first part of the name.
If there is only one atom of the element in
the compound, then you just write the name
of the element.
If there is more than one atom of the
element in the compound, then you use the
appropriate prefix followed by the element’s
name.
Formula to Name:
Covalent
Examples:

NO
 nitrogen

N2O
 dinitrogen

SO
 sulfur

S2O
 disulfur
Formula to Name:
Covalent
For the second element in the
compound, the process is almost
exactly the same.
The only differences are that you use a
prefix even if there is only one atom of
the second element in the compound
and you change the ending of the name
like in ionic compounds.
Formula to Name:
Covalent
Let’s try some!
NO

nitrogen monoxide
N2O4

dinitrogen tetraoxide
SO2

sulfur dioxide
H2O

dihydrogen monoxide
Formula to Name:
Covalent
Questions?
Name to Formula:
Covalent
Due to the use of prefixes to denote
the number of atoms of each element in
a covalent compound, going from name
to formula is actually pretty easy.
Look at the first element named.


If it does not have a prefix, then there is
only one atom.
If it has a prefix, then that is how many
atoms there are.
Name to Formula:
Covalent
The second element in the formula
name should always have a prefix to
identify how many atoms there are.
Simply look at the periodic table and
find the non-metal which has a very
similar name and the prefix will tell you
how many there are.
Name to Formula:
Covalent
Let’s try some!
phosphorus trisulfide

PS3
disulfur dioxide

S2O2
silicon tetrahydride

SiH4
nitrogen monoxide

NO
Name to Formula:
Covalent
Questions?
A Note on Naming
Covalent Compounds
There is one other type of covalent
compound.
Some non-metals do not exist in their
element form, but instead in polyatomic
molecules.
There is a list of these non-metals on
the back of your periodic table.
A Note on Naming
Covalent Compounds
Formula
Name
Formula
Name
H2
hydrogen
N2
nitrogen
Cl2
chlorine
O2
oxygen
F2
fluorine
Br2
bromine
I2
iodine
As2
astatine
P4
phosphorus
S8
sulfur
A Note on Naming
Covalent Compounds
So, if you ever see the name of a nonmetal alone and it is asking for the
formula, check your list of polyatomic
molecules first to make sure you have
the formula correct.