CHAPTER 9: Chemical Names
and Formulas
Objectives:
1. To be able to name ionic and molecular
compounds, and acids.
2. To be able to write the formulas of ionic
and molecular compounds, and acids.
Different Types of Formulas and
Names
• Ionic compounds
• Molecular compounds (molecules)
• Acids (a special type of molecule)
Ionic Compounds
Monatomic ions are ions of a single atom with a positive or
negative charge resulting from the loss or gain of one or
more valence electrons.
Monatomic cations:
Na+, Ca2+
Monatomic anions:
Cl-, N3-
Naming monatomic cations:
Cations for groups 1, 2, & 3
metals have the same name as
the atoms, followed by ion or
cation.
Naming monatomic anions:
Anion start with the same
stem and end with -ide.
This is followed by ion or
anion.
Na+ is sodium ion or sodium
cation.
Cl- is chloride ion or
chloride anion.
Other Names of Monatomic Ions
Ion Symbol
Ion Name
Li+
lithium ion (or cation)
Ca2+
calcium ion (or cation)
Al3+
aluminum ion (or cation)
F-
fluoride ion (or anion)
O2-
oxide ion (or anion)
N3-
nitride ion (or anion)
P3-
phosphide ion (or anion)
Naming Binary Ionic Compounds
Binary Ionic Compounds are composed of ions of
two elements.
To Name Binary Ionic Compounds, place the cation
name first, followed by the anion name.
Formulas
NaCl
CaF2
Mg3N2
AlP
K2Se
Names
sodium chloride
calcium fluoride
magnesium nitride
aluminum phosphide
potassium selenide
Polyatomic Ions
• Polyatomic ions are ions composed of more than
one type of atom (usually nonmentals) covalently
bonded.
• Examples of Polyatomic ions:
NH4+ PO43SO32- OH• For naming polyatomic ions, you can use your
common ion table to get the name.
Compounds
Names
NH4Cl
ammonium chloride
Na3PO4
sodium phosphate
Al2(CO3)3
aluminum carbonate
Cu(NO2)2
copper(II) nitrite
Naming Ions & Ionic Compounds of Transition Metals
• Since some transition metals may have more then one charge, the
charges of the cations must be determined and represented when
naming transition metal ions and compounds with transition
metal ions.
• For example, iron is a transition metal and can have two common
charges, Fe2+ and Fe3+.
• When naming these ions, we use the Stock system which uses
Roman numerals in parentheses after the metal name.
• If the charge of the metal is not given directly, you must
determine it by using the formula given.
Ion
Name of Ion
Ionic Compound Name of Compound
Fe2+ iron(II) ion
FeCl2
iron(II) chloride
Fe3+ iron(III) ion
FeCl3
iron(III) chloride
Cu+ copper(I) ion CuF
copper(I) fluoride
Pb4+ lead(IV) ion
PbI4
lead(IV) iodide
1.
2.
3.
4.
5.
6.
Steps to Writing Formulas of Ionic Compounds
Write the symbols of both ions including their charges
remembering that the cation is placed first followed by the
anion. sodium oxide
Na+ O2Crisscross the value of the charges. This will make it so that
the charges are balanced.
Na+ O2Rewrite your new formula and make sure the charges cancel
each other. Na2O
two Na+ = +2
total charge
one O2- = -2
is zero
If the charge is 1- or 1+, leave the number 1 out the formula
since it is understood to be there.
If necessary, reduce the numbers of each atom by a common
denominator since formula units represent the lowest ratio of
ions in an ionic compound.
If there is more then one polyatomic ion present, use ( ) around
the ion and then place the subscript outside of the ( ).
Formula Practice: Binary Ionic Compounds
Name of Compound
aluminum iodide
calcium phosphide
barium sulfide
rubidium bromide
strontium nitride
copper(II) chloride
chromium(III) oxide
Ions
Al3+
Ca2+
Ba2+
Rb+
Sr2+
Cu2+
Cr3+
IP3S2BrN3ClO2-
Formula
AlI3
Ca3P2
BaS
RbBr
Sr3N
CuCl2
Cr2O3
Naming Ionic Compounds with Transition
Metals
•
It is necessary to determine the charge of a transition metals that can
have more then one charge in order to name it.
• This can be done by using the formula given and determining the
charge of the anion first.
• Remember that the total charges of the anion and cation must cancel
each other out.
Formula
CuCl
CuCl2
Fe2O
Fe2O3
PbO2
PbCO3
Ions
Cu+
Cu2+
Fe2+
Fe3+
Pb4+
Pb2+
ClClO2O2O2CO32-
Name
copper(I) chloride
copper(II) chloride
iron(II) oxide
iron(III) oxide
lead(IV) oxide
lead(II) carbonate
Formula Making: Compounds with
Polyatomic Ions
• Formula making with polyatomic ions is very
similar to what you have learned so far.
• Just DON’T forget to use ( ) around polyatomic
ions when there is more then one of them!
Names
Ions
Formula
magnesium sulfate
Mg2+ SO42MgSO4
ammonium fluoride
NH4+ FNH4Cl
lithium carbonate
Li+
CO32Li2CO3
calcium nitrate
Ca2+ NO3Ca(NO3)2
beryllium hydroxide
Be2+ OHBe(OH)2
Naming Binary Molecular Compounds
• When two nonmetals combine, they form a molecular compound whose
formula shows the actual number of each kind of atom found in a
molecule of the compound.
• To name these compounds, we use a similar method to naming ionic
cmps (see endings) except we can use prefixes to denote number of
Prefixes for Naming Covalent Compounds
each atoms.
Prefix
monoditritetrapentahexaheptaoctanonadeca-
Number of atoms
1
2
3
4
5
6
7
8
9
10
Example
NO
SiO2
SO3
SCl4
SCl5
CBr6
IF7
N3O8
I4O9
S2F10
Name
nitrogen monoxide
silicon dioxide
sulfur trioxide
sulfur tetrachloride
sulfur pentachloride
carbon hexabromide
iodine heptafluoride
trinitrogen octoxide
tetriodine nonoxide
disulfur decafluoride
• Note: when there is only atom of the first element in the compound
mono- is not used before the atom’s name.
• Note: when using prefixes with atoms that start with a vowel, the last vowel
of the prefix is dropped.
Naming Practice: Binary Molecular Cmpds
Formula
Name
NH3
nitrogen trihydride
PCl5
phosphorous pentachloride
SeF6
selenium hexafluoride
NO
nitrogen monoxide
P2O7
diphophorous heptoxide
C3H8
tricarbon octahydrogen
Naming Acids
•
For now, the acids that we will learn how to
name contain hydrogen ions, H+. (formulas start
with H)
Naming Rules:
1. When the anion name ends in -ide, the stem of
the anion name begins with the prefix hydro- and
ends with -ic. The name is then followed by the
word acid.
2. When the anion name ends in -ite, the anion ends
with -ous, followed by the word acid.
3. When the anion name ends in -ate, the anion
name ends with -ic, followed by the word acid.
Naming Acids
Formula
HBr
HCl
HI
H2S
H2SO4
H2SO3
H3PO3
H3PO4
HClO
HClO4
Anion Ending
-ide
-ide
-ide
-ide
-ate
-ite
-ite
-ate
-ite
-ate
Acid Name
hydrobromic acid
hydrochloric acid
hydriodic acid
hydrosulfuric acid
sulfuric acid
sulfurous acid
phosphorous acid
phosphoric acid
hypochlorous acid
perchloric acid