Naming
Compounds and
Writing Formulas
Metals and Nonmetals

For nomenclature purposes, metals are
to the left of the stair step line and
nonmetals are to the right.
Systematic Naming
A compound is made of two or more
elements.
 The name should tell us how many and
what type of atoms.

Types of Compounds

The types of compounds you will learn
how to name and draw are
 ionic compounds (binary and
ternary),
 molecular compounds and
 acids (binary and ternary).
Atoms and Ions
Atoms are electrically neutral.
 They have the same number of protons
and electrons.
 Ions are atoms, or groups of atoms,
with a charge.
 Ions have a different numbers of
electrons.

Anions
negative ion.
An anion is a _________
gained electrons.
 An anion has _______
 Nonmetals can gain electrons.
 The charge is written as a superscript
on the right.

1F
2O
1 electron(s)
Has gained ___
2 electron(s)
Has gained ___
Cations
positive ion.
A cation is a _________
 It is formed by _______
losing electrons.
 There are more protons than electrons.
 Metals form cations.

1+
1 electron(s)
K Has lost ___
2+
2 electron(s)
Has lost ___
Ca
Oxidation Numbers
IONIC COMPOUNDS
Naming Cations

For cations, if the charge is always the
same (Group A) just write the name of
the metal.
Naming Cations

Li1+

lithium
Li is the symbol for ________.

Lithium is a Group 1A metal, so the
charge is always the same. Write
the name of the metal.

Li1+ is called the ___________.
lithium ion
Naming Cations

Sr2+

strontium
Sr is the symbol for __________.

Strontium is a Group 2A metal, so
the charge is always the same.
Write the name of the metal.

Sr2+ is called the _____________.
strontium ion
Naming Cations
Transition metals (as well as tin and
lead) can have more than one type of
charge.
 Indicate the charge with Roman
numerals in parenthesis.
 Zinc (Zn2+) and silver (Ag1+), although
transition metals, only have one
possible charge. Roman numerals ARE
NOT used for zinc and silver.

Naming Cations

Fe2+

Fe is the symbol for ______.
iron

Iron is a transition metal, so the
charge is not always the same.
Write the name of the metal,
indicating the charge with Roman
numerals in parenthesis.

Fe2+ is called the ___________.
iron (II) ion
Naming Cations

Pb2+

Pb is the symbol for ______.
lead

Lead is a Group 4A metal, and the
charge is not always the same.
Write the name of the metal,
indicating the charge with Roman
numerals in parenthesis.

Pb2+ is called the ___________.
lead (II) ion
Problem
1) Name the following cations.
a) Ca2+
Calcium ion
b) Al3+
Aluminum ion
c) Sn4+
Tin (IV) ion
Problem

Name the following ions.
d) Na1+
Sodium ion
e) Fe3+
Iron (III) ion
f) Cu1+
Copper (I) ion
Naming Anions
Naming monatomic anions is always the
same.
 Change the element ending to – ide
 Example: F1 F is the symbol for fluorine, F1- is called
fluor ine.
ide.

Naming Anions

Cl
Cl is the symbol for _________.
chlorine

Chlorine is a Group 7A nonmetal, so
the charge is always the same (-1).

Cl- is called the ____________.
chloride ion
Naming Anions

O2
O is the symbol for _________.
oxygen

Oxygen is a Group 6A nonmetal, so
the charge is always the same (-2).

O2- is called the __________.
oxide ion
Problem
2) Name the following anions.
a) S2-
sulfide ion
b) Br -
bromide ion
Problem
2) Name the following anions.
c) N3d) Se2-
nitride ion
selenide ion
Ionic Compounds
In the formula for an ionic compound,
the symbol of the cation is written before
that of the anion.
 Subscripts, or small numbers written to
the lower right of the chemical symbols,
show the numbers of ions of each type
present in a formula unit.

Naming Binary Ionic
Compounds
Binary ionic compounds are composed
of a metal bonded with a nonmetal.
 Name the metal ion using a Roman
numeral in parenthesis if necessary.
 Follow this name with the name of the
nonmetal ion.

Problem
3) Name the following binary ionic
compounds.
a) NaCl
sodium chloride
b) Ca3P2
calcium phosphide
Problem

Name the following binary ionic
compounds.
c) CuO
d) SnBr2
Copper (II) oxide
Tin (II) bromide
Problem

Name the following binary ionic
compounds.
e) Fe2S3
f) AlF3
Iron (III) sulfide
Aluminum fluoride
Problem

Name the following binary ionic
compounds.
g) KCl
Potassium chloride
h) Na3N
Sodium nitride
Problem

Name the following binary ionic
compounds.
i) CrN
Chromium (III) nitride
j) PbO2
Lead (IV) oxide
Writing Formulas for Cations
Write the formula for the metal.
 If a Roman numeral is in parenthesis
use that number for the charge.
Indicate the charge with a superscript.
 If no Roman numeral is given, find the
Group A metal on the periodic table and
determine the charge from the column
number.

Writing Formulas for Cations

Nickel (II) ion

____
Ni is the symbol for nickel.

Nickel is a transition metal, which is
the reason why the charge with
Roman numerals in parenthesis was
included.

The formula for the nickel (II) ion is
Ni2+
_____.
Writing Formulas for Cations

Gallium ion

____
Ga is the symbol for gallium.

Gallium is a Group 3A metal and its
charge is always the same (+3).

The formula for the gallium ion is
Ga3+
______.
Problem
4) Write the formulas for the following
cations.
a) Magnesium ion Mg2+
b) Copper (II) ion
c) Potassium ion
Cu2+
1+
K
Problem

Write the formulas for the following ions.
d) Silver ion
Ag1+
e) Chromium (VI) ion
f) Mercury (II) ion
6+
Cr
Hg2+
Writing Formulas for Anions
Write the formula for the nonmetal.
 Find the Group A nonmetal on the
periodic table and determine the charge
from the column number.

Writing Formulas for Anions

Phosphide

___
P is the symbol for phosphorus.

Looking at the periodic table and
finding phosphorus, the oxidation
number (charge) can be determined.

The formula for phosphide is _____.
P3-
Writing Formulas for Anions

Bromide

___
Br is the symbol for bromine.

Looking at the periodic table and
finding bromine, the oxidation
number (charge) can be determined.

The formula for bromide is _____.
Br1-
Problem
5) Write the formulas for the following
anions.
As3a) arsenide
b) telluride
2Te
Problem

Write the formulas for the following
anions.
1c) iodide ion I
d) carbide ion
C4-
Writing Formulas for Ionic
Compounds
Oxidation numbers can be used to
determine the chemical formulas for
ionic compounds.
 If the oxidation number of each ion is
multiplied by the number of that ion
present in a formula unit, and then the
results are added, the sum must be
zero.

Writing Formulas for Binary
Ionic Compounds

Write the symbol for the metal.
Determine the oxidation number from
either the column number or the Roman
numeral and write it as a superscript to
the right of the metal’s symbol.
Writing Formulas for Binary
Ionic Compounds

To the right of the metal’s symbol, write
the symbol for the nonmetal. Determine
the oxidation number from the column
number and write it as a superscript to
the right of the nonmetal’s symbol.
Writing Formulas for Binary
Ionic Compounds

Example: potassium fluoride
K
+
F
-
Writing Formulas for Binary
Ionic Compounds

If the two oxidation numbers add
together to get zero, the formula is a
one-to-one ratio of the elements.
Writing Formulas for Binary
Ionic Compounds

Example: potassium fluoride
+
KKFF
-
Writing Formulas for Binary
Ionic Compounds

Example: aluminum sulfide
Al
3+
S
2-
Writing Formulas for Binary
Ionic Compounds

If the two oxidation numbers DO NOT
add together to get zero, you will need
to “criss-cross” the superscripts. These
numbers now become subscripts.
Writing Formulas for Binary
Ionic Compounds

Example: aluminum sulfide
3+
2-
Al 2- S 3+
Writing Formulas for Binary
Ionic Compounds

Omit all positive and negative signs and
omit all 1’s.
Writing Formulas for Binary
Ionic Compounds

Example: aluminum sulfide
AlAl2 2SS3 3
Problem
6) Write the formulas for the following
binary ionic compounds.
a) Lithium selenide
b) Tin (II) oxide
Li2Se
SnO
Problem

Write the formulas for the following
binary ionic compounds.
c) Tin (IV) oxide
SnO2
d) Magnesium fluoride
MgF2
Problem

Write the formulas for the following
binary ionic compounds.
e) Copper (II) sulfide
CuS
f) Iron (II) phosphide
Fe3P2
Problem

Write the formulas for the following
binary ionic compounds.
g) Gallium nitride
GaN
h) Iron (III) sulfide
Fe2S3
Naming Ternary Ionic
Compounds
Ternary ionic compounds are composed
of at least 3 elements.
 Name the metal ion, using a Roman
numeral in parenthesis if necessary.
 Follow this name with the name of the
polyatomic ion.

Polyatomic ions
Polyatomic ions are groups of atoms
that stay together and have a charge.
 Examples are on page 7 of the
Reference Tables for Chemistry and
include:
 Nitrate NO3 Nitrite NO2 Hydroxide OH
Ternary Ionic Compounds
There is one polyatomic ion with a
positive oxidation number (NH4+) that
may come first in a compound. Name
the ion, ammonium.
 Follow this name with the name of the
anion or second polyatomic ion.

Examples
7) Name the following ternary ionic
compounds.
a) LiCN
Lithium cyanide
b) Fe(OH)3 Iron (III) hydroxide
Examples

Name the following ternary ionic
compounds.
c) (NH4)2CO3 Ammonium carbonate
d) NiPO4
Nickel (III) phosphate
Problems

Name the following ternary ionic
compounds.
Sodium nitrate
e) NaNO3
f) CaSO4
Calcium sulfate
Problems

Name the following ternary ionic
compounds.
g) (NH4)2O Ammonium oxide
h) CuSO3
Copper (II) sulfite
Writing Formulas for Ternary
Ionic Compounds

Write the symbol for the metal or
ammonium ion. Write the oxidation
number as a superscript to the right of
the metal’s/ammonium ion’s symbol.
Writing Formulas for Ternary
Ionic Compounds

To the right of the metal’s symbol, write
the symbol for the nonmetal or
polyatomic ion. Write the oxidation
number as a superscript to the right of
the nonmetal’s/polyatomic ion’s symbol.
Writing Formulas for Ternary
Ionic Compounds

Example: potassium nitrate
K
+
NO3
-
Writing Formulas for Ternary
Ionic Compounds

If the two oxidation numbers add
together to get zero, the formula is a
one-to-one ratio of the elements.
Writing Formulas for Ternary
Ionic Compounds

Example: potassium nitrate
+
-
KKNO
NO
33
Writing Formulas for Ternary
Ionic Compounds

Example: aluminum hydrogen sulfate
Al
3+
HSO4
-
Writing Formulas for Ternary
Ionic Compounds
If the two oxidation numbers DO NOT
add together to get zero, you will need
to “criss-cross” the superscripts. These
numbers now become subscripts.
 Parentheses are to be placed around
polyatomic ions before criss-crossing.

Writing Formulas for Ternary
Ionic Compounds

Example: aluminum hydrogen sulfate
3+
-
Al - (HSO4) 3+
Writing Formulas for Ternary
Ionic Compounds

Omit all positive and negative signs and
omit all 1’s.
Writing Formulas for Ternary
Ionic Compounds

Example: aluminum hydrogen sulfate
Al
Al(HSO
(HSO4)33
Problems
8) Write the formulas for the following
ternary ionic compounds.
a) Ammonium chloride NH Cl
4
b) Ammonium sulfide
(NH4)2S
Problems

Write the formulas for the following
ternary ionic compounds.
c) Barium nitrate
Ba(NO )
3 2
d) Zinc iodate
Zn(IO3)2
Problems

Write the formulas for the following
ternary ionic compounds.
e) Sodium hypochlorite NaClO
f) Chromium (III) acetate
Cr(CH3COO)3 or
Cr(C2H3O2)3
Problems

Write the formulas for the following
ternary ionic compounds.
g) Iron (II) dichromate FeCr O
2
h) Mercury (I) bromate
HgBrO3
7
STOP HERE
COVALENT
(Molecular)
COMPOUNDS
Molecular Compounds
Molecular compounds are made of
molecules.
 They are made by joining nonmetal
atoms together into molecules.

Naming is Easier

A molecular compound’s name tells you
the number of atoms through the use of
prefixes.
Prefixes
1 mono 2 di 3 tri 4 tetra 5 penta
6 hexa 7 hepta 8 octa 9 nona 10 deca
Prefixes

The name will consist of two words.
Prefix name prefix name -ide

One exception is we don’t write
mono- if there is only one of the first
element.
Prefixes

The following double vowels cannot be
used when writing names:
 (oa)
 (oo)
Example

NO2

There is one nitrogen


mononitrogen
But, you cannot use mono- on the first
element, so drop the prefix.
 nitrogen
mononitrogen
Example

NO2

There are two oxygens

dioxygen
Example

NO2


dioxygen
You need the suffix -ide

diox ygen
ide
Example

NO2

nitrogen dioxide
Example

N2O

There are two nitrogens


dinitrogen
There is one oxygen

monooxygen
Example

N2O


monooxygen
You cannot run (oo) together, so

monoxygen
Example

N2O


monoxygen
You need the suffix -ide

monoxygen
ide
Example

N2O

dinitrogen monoxide
Problem
9) Name the following molecular
compounds.
a) Cl2O7
b) CBr4
dichlorine heptoxide
carbon tetrabromide
Problem

Name the following molecular
compounds.
c) CO2
carbon dioxide
d) BCl3
boron trichloride
Naming Molecular
Compounds
You will not need to criss-cross
oxidation numbers.
 Molecular compounds name tells you
the number of atoms through the use of
prefixes.

Example

diphosphorus pentoxide

The name implies there are 2
phosphorous atoms and 5 oxygens.
P2O5
Example

sulfur hexaflouride

The name implies there is 1 sulfur
atom and 6 fluorines.
SF6
Problem
10) Write the formulas for the following
molecules.
a) tetraiodine nonoxide I O
4 9
b) nitrogen trioxide
NO3
Problem

Write the formulas for the following
molecules.
c) carbon tetrahydride CH
4
d) phosphorus trifluoride
PF3
Types of Compounds
Smallest
piece
Types of
elements
State
Melting
Point
Ionic
Molecular
Formula Unit
Molecule
Metal and
nonmetal
Nonmetals
Solid
Solid, liquid
or gas
High >300ºC
Low <300ºC
Acids
Writing Names and Formulas
Acids
Acids are compounds that give off
hydrogen ions (H+) when dissolved in
water.
 Acids will always contain one or more
hydrogen ions next to an anion.
 The anion determines the name of the
acid.

Naming Binary Acids
Binary acids contain hydrogen and an
anion whose name ends in –ide.
 When naming the acid, put the prefix
hydro- and change -ide to -ic acid.

Example
 HCl

The acid contains the hydrogen ion
and chloride ion.

Begin with the prefix hydro-, name
the nonmetallic ion and change -ide
to -ic acid.
hydrochloride
ic acid
Example
 H2S

The acid contains the hydrogen ion
and sulfide ion.

Begin with the prefix hydro- and
name the nonmetallic ion.
hydrosulfide
Example
 H2S

The next step is change -ide to -ic
acid, but for sulfur the “ur” is added
before -ic.
hydrosulfide
ur ic acid
Problem
11. Name the following binary acids.
a) HF
(hydrofluoric acid)
b) H3P
(hydrophosphoric acid)
Writing the Formulas for
Binary Acids
The prefix hydro- lets you know the acid
is binary.
 Determine whether you need to crisscross the oxidation numbers of
hydrogen and the nonmetal.

Example
 Hydrobromic

acid
The acid contains the hydrogen ion
and the bromide ion.
Example
 Hydrobromic
acid
1+
1H Br

The two oxidation numbers add
together to get zero.
HBr
Example
 Hydrotelluric
acid
The prefix hydro- lets you know the
acid is binary.
 The acid contains the hydrogen ion
and the telluride ion.

Example
 Hydrotelluric
acid
1+
2H Te

The two oxidation numbers do NOT
add together to get zero, so you must
criss-cross.
H2Te
Problem
12) Write the formulas for the following
binary acids.
a) Hydrocyanic acid HCN
b) Hydroselenic acid
H2Se
Naming Ternary Acids
The acid is a ternary acid if the anion
has oxygen in it.
 The anion ends in -ate or -ite.
 Change the suffix -ate to -ic acid
 Change the suffix -ite to -ous acid
 The hydro- prefix is NOT used!

Example
 HNO3

The acid contains the hydrogen ion
and nitrate ion.

Name the polyatomic ion and
change -ate to -ic acid.
nitrate
ic acid
Example
 HNO2

The acid contains the hydrogen ion
and nitrite ion.

Name the polyatomic ion and
change -ite to -ous acid.
nitrite
ous acid
Example
 H3PO4

The acid contains the hydrogen ion
and phosphate ion.

Name the polyatomic ion and
change -ate to -ic acid.
phosphate
oric acid
Problem
13) Name the following ternary acids.
a) H2CO3
(carbonic acid)
b) H2SO4
(sulfuric acid)
Problem
Name the following ternary acids.
c) H2CrO4
d) HClO2
(chromic acid)
(chlorous acid)
Writing the Formulas for
Ternary Acids
The lack of the prefix hydro- from the
name implies the acid is ternary, made
of the hydrogen ion and a polyatomic
ion.
 Determine whether you need to crisscross the oxidation numbers of
hydrogen and the polyatomic ion.

Example

Acetic acid
The polyatomic ion must end in –ate
since the acid ends in -ic.
 The acid is made of H+ and the acetate
ion.

1+
H C
1H
O
2 3 2
Example
1+
H C
1H
O
2 3 2

The two charges when added equal
zero.
HC2H3O2
Example

Sulfurous acid

Again the lack of the prefix hydroimplies the acid is ternary, made of the
hydrogen ion and a polyatomic ion.
Example

sulfurous acid
The polyatomic ion must end in –ite
since the acid ends in -ous.
 The acid is made of H+ and the sulfite
ion.

1+
2H SO3
Example
1+
2H SO3

The two charges when added do not
equal zero, so you must crisscross the
oxidation numbers.
Example
1+
2H SO3

Ignore the negative sign and ones are
understood.
H2SO3
Problem
14) Write the formulas for the following
ternary acids.
a) perchloric acid HClO
4
b) iodic acid
HIO3
Problem

Write the formulas for the following
ternary acids.
c) dichromic acid
H Cr O
2
d) hypochlorous acid
2
7
HClO