Chapter 9
Naming Simple Compounds
Monatomic Ions
Ionic compounds consists of a positive metal ion and a
negative nonmetal ion combined in a proportion such that
their charges add up to a net charge of zero.
NaCl – consists of one Na+ and one Cl-.
Monatomic ions consists of a single atom with a positive
or negative charge resulting from the loss or gain of one
or more valence electrons. These are seen as elements
on the Periodic Table which become ions.
Monatomic Ions - Cations
Cations tend to lose valence electrons. (1+ charge – lose
1 electron, 2+ charge – lose 2 electrons, etc. )
When the metals in Groups 1A, 2A, and 3A lose
electrons, they form cations with positive charges equal
to their group number.
The name of the cations of the Group 1A, 2A and 3A are
the same as the name of the metal, followed by the word
ion or cation.
Na+ is sodium ion, Ca2+ is calcium ion, Al3+ is aluminum
ion.
Monatomic Ions - Anions
Nonmetals tend to gain electrons for form anions, so the
charge of a nonmetallic ion is negative.
The charge of any ion of a Group A nonmetal is
determined by subtracting 8 from the group number.
Group 7A form anions with a 1- charge (7-8 = -1)
Anion names start with the stem of the element name
and end in –ide.
Anion of fluorine is fluoride ion (F-), anion of chlorine is
chloride ion (Cl-)
Ions of Transition Metals
Many of the transition metals (Group 1B – 10B) form
more than one cation with different ionic charges.
Two methods are used to name these ions.
•Stock System – a Roman numeral in parentheses is
placed after the name of the element to indicate the
numerical value of the charge.
Fe2+ is iron(II) ions
Fe3+ is iron(III) ion.
•Classical – name of the element is used to form the root
name for the element. This system is useful only if there
only two ions! (Remember: -ic is higher than -ous)
Fe2+ is ferrous ion
Fe3+ is ferric ions
Fe2+
iron(II) / ferrous
Ag1+
silver
Fe3+
iron(III) / ferric
Cd2+
cadmium
Zn2+
zinc
Au1+
gold(I) / aurous
Au3+
gold(III) / auric
Co2+
cobalt(II) /
cobaltous
Co3+
cobalt(III) /cobaltic
Cr2+
chromium(II) /
chromous
Cr3+
chromium(III)
/chromic
Hg1+
Hg2+
mercury(I) / mercurous
mercury(II) / mercuric
Mn2+
manganese(II)
Mn3+
manganese(III)
Mn4+
manganese(IV)
Ni2+
nickel(II) / nickelous
Ni3+
nickel(III) / nickelic
Pb2+
lead(II) /plumbous
Cu1+
copper(I) / cuprous
Pb4+
lead(IV) / plumbic
Cu2+
copper(II) /cupric
Polyatomic Ions
Polyatomic Ions are charged particles composed of
more than one atom tightly bound together.
Sulfate ions (SO42-) is composed of one sulfur atom and
four oxygen atoms. It is not a combination of one Sulfur
ion and two Oxygen ions!
Polyatomic ions are a tightly bound group of atoms that
behave as a unit and carry a charge.
The names of most polyatomic anions often end in –ite or
–ate.
-1 CHARGE
+1 CHARGE
ion
ion
NH4+
H3 O
Hg2
+
2+
name
name
H2PO3-
dihydrogen phosphite
H2PO4-
dihydrogen phosphate
HCO3-
hydrogen carbonate
HSO3-
hydrogen sulfite
HSO4-
hydrogen sulfate
NO2-
nitrite
NO3-
nitrate
OH-
hydroxide
CH3COO-
acetate
ammonium
hydronium
mercury(I)
-1 CHARGE
-1 CHARGE
ion
ion
name
name
CrO2-
chromite
BrO-
hypobromite
CN-
cyanide
BrO2-
bromite
CNO-
cyanate
BrO3-
bromate
CNS-
thiocyanate
BrO4-
perbromate
O2 -
superoxide
IO-
hypoiodite
MnO4-
permanganate
IO2-
iodite
hypochlorite
IO3-
iodate
chlorite
IO4-
periodate
chlorate
AlO2-
aluminate
perchlorate
N3 -
azide
ClO
-
ClO2
-
ClO3
-
ClO4
-
-2 CHARGE
ion
HPO32-
HPO42-
CO3
2-
name
hydrogen
phosphite
hydrogen
phosphate
carbonate
SO32-
sulfite
SO4
sulfate
2-
S 2O 3
2-
SiO32-
-2 CHARGE
thiosulfate
silicate
ion
name
C22-
carbide
C2O42-
oxalate
CrO42-
chromate
Cr2O72-
dichromate
C4H4O62-
tartrate
MoO42-
molybdate
O22-
peroxide
S22-
disulfide
-3 CHARGE
ion
-4 CHARGE
name
PO33-
phosphite
PO43-
phosphate
PO23-
hypophosphite
AsO33-
arsenite
AsO43-
arsenate
ion
P2O74-
name
pyrophosphate
End of Section 9.1
Naming Binary Ionic Compounds
A binary compound is composed of two elements (in
any proportion) and can be either ionic or molecular
(covalent)
To name any binary ionic compound, place the cation
name first, followed by the anion name.
Cs2O is cesium oxide
Cu2O is copper(I) oxide
NaBr is sodium bromide
CuO is copper(II) oxide
H2O is a covalent compound (Chpt 8) called water.
Writing Formulas
Binary Ionic Compounds
Write the symbol of the cation and then the anion. Add
whatever subscripts are needed to balance the charges.
The positive charge of the cation must balance the negative
charge of the anion so that the net ionic charge of the formula
is zero.
K+ + Cl-  KCl
Ca2+ + Br-  CaBr2
Fe3+ + O2-  Fe2O3
Use the crisscross method – the numerical value of the
charge of each ion is crossed over and becomes the subscript
for the other ion. Bring subscripts to lowest whole ratio!
Writing Formulas
Polyatomic Ionic Compounds
An –ate or –ite ending on the name of a compound indicates
that the compound contains a polyatomic anion that includes
oxygen.
Write the symbol for the cation followed by the formula for the
polyatomic ion and balance the charges.
Ca2+ + NO3-  Ca(NO3)2
Sr2+ + SO32-  SrSO3
Li+ + CO32-  Li2CO3
Use the crisscross method – the numerical value of the
charge of each ion (polyatomic too) is crossed over and
becomes the subscript for the other ion.
Naming
Polyatomic Ionic Compounds
First recognize that the compound contains a polyatomic
ion.
State the cation first and then the anion
NaClO
sodium hypochlorite
(NH4)2C2O4
ammonium oxalate
Li2CO3
lithium carbonate
End of Section 9.2
Naming Molecular Compounds
Binary ionic compounds are composed of the ions of two
elements, a metal and a nonmetal.
Binary molecular compounds are composed of two
elements, two nonmetals and they are not ions.
Binary molecular compounds are composed of atoms,
not ions, so ionic charges cannot be used to write
formulas or to name them.
In addition, when two nonmetallic elements combine, the
often do so in more than one way. (CO, CO2)
Prefixes in the names of binary molecular compounds
help distinguish compounds containing different amounts
of the same two elements.
Naming Molecular Compounds
The prefix in the name of a binary molecular compound
tells how many atoms of each element are present in
each molecule of the compound.
Prefix
Number
mono-
1
di-
2
tri-
3
tetra-
4
penta-
5
hexa-
6
hepta-
7
octa-
8
nona-
9
deca-
10
Naming Molecular Compounds
The names of all binary molecular compounds end in
–ide.
CO is carbon monoxide
CO2 is carbon dioxide
If just one atom of the first element is in the formula, omit
the prefix mono•Name the elements in order listed in the formula
•Use prefixed to indicate the number of each kind of atom
•The suffix of the name of the second element is –ide.
N2O is dinitrogen monoxide
SF6 is sulfur hexafluoride.
Writing Formulas
Molecular Compounds
Use the prefixes in the name to tell you the subscript of
each element in the formula.
Then write the correct symbols for the two elements with
the appropriate subscripts.
Silicon Carbide
SiC
Dinitrogen tetroxide
N 2O 4
Diphosphorus trioxide
P2O3
End of Section 9.3
End of Chapter 7
Naming Acids
Acid is a compound that contains one or more hydrogen
atoms and produces hydrogen ions (H+) when dissolved
in water.
When naming acids, the acid consists of an anion
combined with as many hydrogen ions s are needed to
make the molecule electrically neutral.
The general chemical formulas of acids is HnX.
X is a monatomic or polyatomic anion
n is a subscript indication the number of hydrogen ions
combined with the anion.
Naming Acids
Three rules are used to name acids. The name depends
on the name of the anion and its suffix (-ide, -ite, -ic)
1.a. When the name of the anion ends in –ide, the acid
name begins with the prefix hydro-.
b. The stem of the anion has the suffix –ic and is followed
by the word acid.
H+
+
Hydrogen ion
H+
Hydrogen ion
Clchlor ide ion
+
S2sulfide ion

HCl
hydrochlor
ic acid
hydro

H 2S
hydrosulfur
ic acid
hydro
Naming Acids
Three rules are used to name acids. The name depends
on the name of the anion and its suffix (-ide, -ite, -ic)
1.a. When the anion name ends in –ite, the acid name
is the stem of the anion with the suffix –ous, followed
by the word acid
H+
+
Hydrogen ion
H+
Hydrogen ion
SO32sulfite ion
+
IO2iodite ion

H2SO3
sulfurous acid

HIO2
iod ous acid
Naming Acids
Three rules are used to name acids. The name depends
on the name of the anion and its suffix (-ide, -ite, -ic)
1.a. When the anion name end in –ate, the acid name is
the stem of the anion with the suffix –ic followed by the
word acid.
H+
+
Hydrogen ion
H+
Hydrogen ion
NO3nitrate ion
+
SO42sulfate ion

HNO3
nitr ic acid

H2SO4
sulfuric acid
Writing Formulas for Acids
Use the rules for writing the names of acids in reverse to
write the formula for acids.
Hydrobrom
ic acid
Hydro
Hydro indicates the bromide ion
HBr
Phosphorous acid
-ous indicates the phosphite ion
H3PO3
Formic acid
-ic and beginning with the anion name indicates the formate ion
HCOOH
Bases
A base is an ionic compound that produced hydroxide
ions (OH-)when dissolved in water.
Bases are named the same way as other ionic
compounds – the name of the cation is followed by the
name of the anion.
NaOH is sodium hydroxide
To write the formulas for bases, write the symbol for the
cation followed by the formula for the hydroxide ion.
(balance the ionic charges jusat as you do for any ionic
compound)
Aluminum hydroxide – Al3+ + OH-  Al(OH)3
Ammonium hydroxide – NH4+ + OH-  NH4OH
End of Section 9.4
End of Chapter 7
Laws Governing Formulas & Names
Law of Definite Proportions
A chemical formula tells you (by subscripts) the ratio of
atoms of each element in the compound.
Ratios of atoms can also be expressed as ratios of
masses.
100 g of MgS breaks down into 43.12g Mg and 56.88g of
sulfur.
100g MgS 1 mol MgS 1 mol Mg
24.305g Mg = 43.12g Mg
56.4g MgS 1 mol MgS 1 mol Mg
100g MgS 1 mol MgS 1 mol S
32.06g S = 56.88g S
56.4g MgS 1 mol MgS 1 mol S
Laws Governing Formulas & Names
The ratios of these masses is 43.12/56.88 = 0.758:1
The mass ratio of 0.758:1 does not change no matter how
the magnesium sulfide is formed or the size of the sample.
Law of Definite proportions states that in samples of
any chemical compound, the masses of the elements are
always in the same proportions.
MgS illustrates the law of definite proportions
Laws Governing Formulas & Names
The Law of Multiple Proportions
Water (H2O) and hydrogen peroxide (H2O2) are formed
by the same two elements, they have different physical
and chemical properties.
Each compound obeys the law of definite proportions in
every sample of hydrogen peroxide. (16g O : 1g H)
In every sample of water, the mass ratio of O to H is
always 8:1 (8g O: 1g H)
If a sample of H2O2 has the same mass of H as a sample
of H2O, the ratio of the mass of O in the two compounds
is exactly 2:1
Laws Governing Formulas & Names
16 g O (in H2O2 has 1g H)
8 g O (in H2O has 1 g H)
= 16 = 2 = 2:1
8
1
Law of multiple proportions states that whenever the
same two elements form more than one compound, the
different masses of one element that combine with the
same mass of the other element are in the ratio of small
whole numbers.
End of Chapter 9