
Name to Formula
◦ 1. Write the cation first (include charge)
◦ 2. Write the anion second (include charge)
◦ 3. “Swap and drop” the charges to determine how
many of each ion are needed
◦ 4. Make sure the total charge of the compound is 0
 (The final formula will NOT have + or – in it.)
◦ 5. Rewrite the formula without charges

Lithium oxide
“Oxide” ends in –ide
and is not found on
the polyatomic ion
chart. We know the
charge is 2- because
of where oxygen is
found on the periodic
table.
◦ 1. Cation (including charge): Li+
◦ 2. Anion (including charge): O2◦ 3. Swap and drop charges:
 Li+
O2-
 Li+2

O2Li2O
There is are two
lithium cations and
one oxide anion.
1
The formula is neutral:
Li: +1 x 2 = +2 charge
O: -2 x 1 = -2 charge
0 total charge

Barium nitrate
Ba2+
◦ 1. Cation (including charge):
◦ 2. Anion (including charge): NO3◦ 3. Swap and drop charges:
 Ba2+
NO3 Ba2+1
NO3- 2

Ba(NO2)2
There is one barium
cation and two
nitrate anions.
“Nitrate” is a
polyatmic ion whose
name you should
have memorized.
The formula is neutral:
Ba: +2 x 1 = +2 charge
NO3: -1 x 2 = -2 charge
0 total charge
The parentheses
show that there are
two nitrate ions.

Aluminum sulfate
◦ 1. Cation (including charge): Al3+
◦ 2. Anion (including charge): SO42◦ 3. Swap and drop charges:
 Al3+
SO42 Al3+ 2
SO42- 3

“Sulfate” is a
polyatmic ion whose
name you should
have memorized.
The formula is neutral:
Al: +3 x 2 = +6 charge
SO4: -2 x 3 = -6 charge
0 total charge
Al2 (SO4)3
There are two
aluminum cations
and three sulfate
anions.
The parentheses
show that there are
three sulfate ions.

Sodium chloride
◦ 1. Cation (including charge): Na+
◦ 2. Anion (including charge): Cl◦ 3. Swap and drop charges:
 Na+
Cl-
 Na+1
Cl-1

NaCl
There is one sodium
cation and one
chloride anion.
“Chloride” ends in
–ide and is not found
on the polyatomic
ion chart. We know
the charge is 1because of where
chlorine is found on
the periodic table.
The formula is neutral:
Na: +1 x 1 = +1 charge
Cl: -1 x 1 = -1 charge
0 total charge

Aluminum oxide
◦ 1. Cation (including charge): Al3+
◦ 2. Anion (including charge): O2◦ 3. Swap and drop charges:
 Al3+
O2-
 Al3+ 2
O2- 3

Al2 O3
There are two
aluminum cations
and three oxide
anions.
“Oxide” ends in –ide
and is not found on
the polyatomic ion
chart. We know the
charge is 2- because
of where oxygen is
found on the periodic
table.
The formula is neutral:
Al: +3 x 2 = +6 charge
O: -2 x 3 = -6 charge
0 total charge

Ammonium nitrate
◦ 1. Cation (including charge): NH4+
◦ 2. Anion (including charge): NO3◦ 3. Swap and drop charges:
 NH4+
NO3 NH4+1
NO3- 1

NH4NO3
There is one
ammonium cation
and one nitrate
anion.
“Ammonium” and
“nitrate” are
polyatmic ions whose
names you should
have memorized.
The formula is neutral:
NH4: +1 x 1 = +1 charge
NO3: -1 x 1 = -1 charge
0 total charge
Parentheses are not
needed because
there is only one of
each polyatomic ion.

Calcium hydroxide
Ca2+
◦ 1. Cation (including charge):
◦ 2. Anion (including charge): OH◦ 3. Swap and drop charges:
 Ca2+
OH-
 Ca2+1
OH- 2

Ca(OH)2
There is one calcium
cation and two
hydroxide anions.
“Hydrocide” is a
polyatmic ion whose
name you should
have memorized.
The formula is neutral:
Ca: +2 x 1 = +2 charge
OH: -1 x 2 = -2 charge
0 total charge
The parentheses
show that there are
two hydroxide ions.

Barium chloride
◦ 1. Cation (including charge): Ba2+
◦ 2. Anion (including charge): Cl◦ 3. Swap and drop charges:
 Ba2+
Cl-
 Ba2+1
Cl- 2

BaCl2
There is one barium
cation and two
chloride anions.
“Chloride” ends in
–ide and is not found
on the polyatomic
ion chart. We know
the charge is 1because of where
chlorine is found on
the periodic table.
The formula is neutral:
Ba: +2 x 1 = +2 charge
Cl: -1 x 2 = -2 charge
0 total charge

Magnesium oxide
◦ 1. Cation (including charge): Mg2+
◦ 2. Anion (including charge): O2◦ 3. Swap and drop charges:
 Mg2+
O2-
 Mg2+2
O2-2

Mg2O2

MgO
“Oxide” ends in –ide
and is not found on
the polyatomic ion
chart. We know the
charge is 2- because
of where oxygen is
found on the periodic
table.
The formula is neutral:
Mg: +2 x 2 = +4
charge
Cl: -2 x 2 = -4 charge
0 total charge
The smallest possible ratio is
1:1, not 2:2. There is one
magnesium cation and one
oxide anion.

Lead (II) nitride
◦ 1. Cation (including charge): Pb2+
◦ 2. Anion (including charge): N3◦ 3. Swap and drop charges:
 Pb2+
N3-
 Pb2+3
N3- 2

Pb3N2
There are three lead
(II) cations and two
nitride anions.
The Roman numeral
tells us that lead has a
charge of +2.
“Nitride” ends in –ide
and is not found on
the polyatomic ion
chart. We know the
charge is -3 because
of where nitrogen is
found on the periodic
table.
The formula is neutral:
Pb: +2 x 3 = +6
charge
N: -3 x 2 = -6 charge
0 total charge

Formula to Name
◦ 1. Determine the charge of the cation (+)
◦ 2. Determine the charge of the anion (-)
◦ 3. Write the name of the cation
 Use element name or polyatomic cation name
 Include Roman numeral if necessary
 D-block
 NOT Ag+, Cd2+, or Zn2+
◦ 4. Write the name of the anion
 -ide or from the polyatomic ion chart
Cation charge: Sr has a
charge of 2+. We know this
because it is located in Group
2 on the periodic table.
Anion charge: ClO2 has a
charge of -1. It is a
polyatomic ion. There are
two of them so the -1 charge
balances out the 2+ charge
of Sr2+.
Name: Chlorite
Name: Strontium
Sr(ClO2)2

Strontium chlorite
Strontium does NOT need a
Roman numeral because it is
found in the s-block. Only
d-block elements and some
p-block elements need
Roman numerals.
Cation charge: Cu is found in
the d-block and can form
more than one ion. Its
charge in this compound will
be +1 to balance Cl-.
Name: Copper (I)

Anion charge: Cl has a charge
of -1. We know this because
it is located in Group 17 on
the periodic table. The name
will end in –ide.
CuCl
Copper (I) chloride
Copper DOES need a Roman
numeral because it is found
in the d-block. The +1
charge tells us what Roman
numeral to use.
Name: Chloride
Cation charge: Pb is found in
the lower-left p-block and
can form more than one ion.
Its charge in this compound
will be +2 to balance the two
NO3- ions.
Name: Lead (II)
Lead (II) nitrate
Anion charge: NO3 has a
charge of -1. It is a
polyatomic ion. There are
TWO of them for a total
negative charge of -2.
Pb(NO3)2
Lead DOES need a Roman
numeral because it is found
in the lower-left p-block.
The +2 charge tells us what
Roman numeral to use.
Name: Nitrate
Cation charge: Pb is found in
the lower-left p-block and
can form more than one ion.
Its charge in this compound
will be +3 to balance the two
NO3- ions.
Name: Lead (III)
Lead (III) nitrate
Anion charge: NO3 has a
charge of -1. It is a
polyatomic ion. There are
THREE of them for a total
negative charge of -3.
Pb(NO3)3
Lead DOES need a Roman
numeral because it is found
in the lower-left p-block.
The +3 charge tells us what
Roman numeral to use.
Name: Nitrate
Anion charge: I has a charge
of -1. We know this because
it is located in Group 17 on
the periodic table. The name
will end in –ide.
Cation charge: K has a charge
of +1. We know this because
it is located in Group 1 on
the periodic table.
Name: Iodide
Name: Potassium
KI
Potassium Iodide
Potassium does NOT need a
Roman numeral because it is
found in the s-block. Only
d-block elements and some
p-block elements need
Roman numerals.