Name
Pre-AP Chemisry: Ionic Bonding and Nomenclature Notes
Class Period
Ionic Bonding
Text Reference: 176-178
Covalent versus Ionic Bonding
So far in our discussion of chemical bonding, we have learned mainly about covalent
bonding. In covalent bonding, pairs of valence electrons are
between
atoms to form molecules. The valence electrons may be shared
(nonpolar
covalent bond) or
(polar covalent bond). Covalent bonding usually results
from the bonding of two or more
.
Today we are going to look at ionic bonding. Ionic bonding involves the
of valence electrons. One atom loses one or more valence electrons to become a
.
The other atom gains one or more electrons to form an
. Ionic compounds
are electrically neutral. This means the total number of negative charges is
to the total number of positive charges. The chemical formula for an ionic compound is
referred to as a formula unit (not a molecule!). Ionic bonding usually results from the
bonding of a
to a
.
Using Lewis Dot Diagrams to Predict Formulas for Ionic Compounds
Lewis dot diagrams can be used to illustrate the transfer of electrons that occurs and to
predict the chemical formula for an ionic compound.
Example 1. Use Lewis dot diagrams to predict the formula for the ionic compound
formed from sodium and chlorine.
1.
Draw Lewis dot diagrams for sodium and for chlorine.
Na
2.
Cl
The sodium atom has one valence electron. The chlorine atom has seven valence
electrons. The chlorine atom only needs one more valence electron in order to have
an octet. The sodium atom will transfer its one valence electron to the chlorine
atom.
Na
+
Cl
→
Na+ +
Sodium ion
3.
Cl
-
Chloride ion
The compound formed will be called sodium chloride. One formula unit of sodium
chloride contains one sodium ion and one chloride ion. The resulting chemical
formula is NaCl.
1
Example 2. Use Lewis dot diagrams to predict the formula for the ionic compound formed
from calcium and iodide.
1.
Draw the Lewis dot diagrams for calcium and iodine.
Ca
2.
I
The calcium atom has two valence electrons. The iodine atom has seven valence
electrons. The iodine atom only needs one more valence electron to have an octet.
The calcium atom will transfer one of its valence electrons to the iodide atom. But
what about the other valence electron? Another iodide atom will be needed.
I
Ca
3.
+
→
I
Ca2+
+
Calcium ion
I
-
+
I
-
Iodide ions
The compound formed will be called calcium iodide. One formula unit of calcium
iodide contains one calcium ion and two iodide ions. The resulting chemical formula
is CaI2.
Example 3. Use Lewis dot diagrams to predict the formula for the ionic compound formed
from barium and sulfur.
1.
Draw the Lewis dot diagrams for barium and sulfur.
Ba
2.
S
The barium atom has two valence electrons. The sulfur has six valence electrons.
The sulfur atom only needs two more electrons to have an octet. The barium atom
will transfer its two valence electrons to the sulfur atom.
Ba
+
S
Ba2+
→
Barium ion
3.
+
S
2-
Sulfide ion
The compound formed will be called barium sulfide. One formula unit of barium
sulfide contains one barium ion and one sulfide ion. The resulting chemical formula is
BaS.
2
You Try It
1.
Use Lewis dot diagrams to predict the formula for the ionic compound formed from
lithium and oxygen.
Chemical Formula
2.
Use Lewis dot diagrams to predict the formula for the ionic compound formed from
aluminum and nitrogen.
Chemical Formula
3.
Use Lewis dot diagram to predict the formula for the ionic compound formed from
magnesium and nitrogen.
Chemical Formula
3
Crystal Lattices
At room temperature, crystals of ionic compounds exist as regular, three-dimensional
arrangements of cations and anions held together by electrostatic attractions. These
arrangements are called crystal lattices. Here is an example of the crystal lattice for
sodium chloride. (Note: The lines between the ions ARE NOT bonds; they are reference
lines showing the relative position of Na+ and Cl-.)
Naming and Writing Formulas for Ionic Compounds
Text Reference: 203-210
Previously you learned how to name and write formulas for binary molecular compounds.
Today you are going to learn how to name and write formulas for ionic compounds. The
common system for naming ionic compounds is a little different because GREEK PREFIXES
ARE NOT USED. Ionic compounds are composed of cations and anions. They are named
by writing the name of the cation followed by the name of the anion.
Naming and Writing Symbols for Monatomic Ions.
Before we can write formulas for binary ionic compounds, we must review how to
determine the name and symbol for a monatomic ion (ion formed from a single atom).
Anions
Anions are negatively charged ions formed when an atom gains electrons. They are usually
formed from nonmetallic elements. The names of monatomic anions end in -ide.

Elements in Group 15 have five valence electrons. They gain 3 electrons and form
anions with a -3 charge.
Ex.
N3nitride ion

Elements in Group 16 have six valence electrons. They gain 2 electrons and form
anions with a -2 charge.
Ex.
O2oxide ion
4

Elements in Group 17 have seven valence electrons. They gain 1 electron and form
anions with a -1 charge.
Ex.
Ffluoride ion
Cations
Cations are positively charged ions formed when an atom loses electrons. They are usually
formed from metallic elements.

Elements in Group 1 have one valence electron. They lose 1 electron and form cations
with a +1 charge.
Ex.
Li+
lithium ion

Elements in Group 2 have one valence electron. They lose 2 electrons and form
cations with a +2 charge.
Ex.
Mg2+ magnesium ion

There are a few elements which are not in groups 1 or 2 that you need to memorize.
Al3+
aluminum ion
Zn2+
zinc ion
2+
+
Cd
cadmium ion
Ag
silver ion

There are some elements (usually transition metals) that form more than one common
ion. A Roman numeral is used to indicate the charge on the ion when naming the ions
formed by these elements.
Fe2+
Iron(II) ion
Fe3+ Iron(III) ion
Cu+
Copper(I) ion
Cu2+
Copper(II) ion
Hg22+
Mercury(I) ion
Hg2+
Mercury(II) ion
2+
4+
Pb
Lead(II) ion
Pb
Lead(IV) ion
Sn2+
Tin(II) ion
Sn4+
Tin(IV) ion
Cr2+
Chromium(II) ion
Cr3+
Chromium(III) ion
Mn2+
Manganese(II) ion
Mn3+
Manganese(III) ion
Co2+
Cobalt(II) ion
Co3+
Cobalt(III) ion
Ni2+
Nickel(II) ion
Ni3+
Nickel(III) ion
You Try It
Complete the following table.
Symbol of Ion
Name of Ion
Sulfide ion
+
Cu
Barium ion
3+
Al
Iron(III) ion
+
Li
Phosphide ion
Cr6+
Chromium(VI) ion
Number of Electrons Lost or Gained
5
Writing Formulas for Binary Ionic Compounds
Ionic compounds are electrically neutral. This means that the total number of positive
charges equals the total number of negative charges. Ionic compounds are always written
in the lowest whole-number ratio of ions. See if you can determine how to balance charges
based upon the following examples.
1.
Lithium fluoride
Li+, FLiF
+
22.
Lithium oxide
Li , O
Li2O
+
33.
Lithium nitride
Li , N
Li3N
2+
4.
Barium chloride
Ba , Cl
BaCl2
2+
25.
Barium sulfide
Ba , S
BaS
2+
36.
Barium phosphide
Ba , P
Ba3P2
2+
7.
Iron(II) iodide
Fe , I
FeI2
2+
28.
Iron(II) oxide
Fe , O
FeO
2+
39.
Iron(II) nitride
Fe , N
Fe3N2
4+
10.
Tin(IV) chloride
Sn , Cl
SnCl4
4+
211.
Tin(IV) sulfide
Sn , S
SnS2
4+ 312.
Tin(IV) phosphide
Sn , P
Sn3P4
You Try It
Write the formulas for the following binary ionic compounds. Hint: First determine the
symbols for the ions involved. Always write the cation first. The first one has been done
for you as an example.
1.
Sodium bromide
2.
Magnesium sulfide
3.
Copper(I) chloride
4.
Calcium bromide
5.
Strontium fluoride
6.
Sodium oxide
7.
Lead(II) bromide
8.
Zinc sulfide
9.
Aluminum oxide
10.
Chromium(VI) nitride
Na+, Br-
6
NaBr
Naming Binary Ionic Compounds
As you can see from the examples above, naming binary ionic compounds is fairly easy. The
only tricky part about naming binary ionic compounds involves the use of the Roman
numerals. There are two things you must consider:
1.
When do you use a Roman numeral when naming a compound?
You use a Roman numeral when the metallic element forms more than one common
ion. This is common of the transition metals. Never use Roman numerals when the
metallic element is from Group 1, Group 2, or with aluminum, cadmium, zinc, or silver.
2.
How do I determine the charge of the Roman numeral?
To determine the charge of the Roman numeral you have to work backwards and
identify the ions making up the compound.
Examples
a.
FeCl2
You know that the chloride ion has a charge of -1. There
are two chloride ions, so the total negative charge is -2.
This means that the total positive charge must be +2. The
compound must have been formed from Fe2+, Cl-. The name
of the compound is Iron(II) chloride
b.
Fe2O3
Since both elements have a subscript, you can just uncross
the charges. This compound was made from Fe3+, O2-. The
name of the compound is Iron(III) oxide
c.
Cu2S
You know that the sulfide ion has a charge of -2. That
means the total positive charge must equal +2. Since
there are two coppers written in the formula, each copper
ion must have a charge of +1. The compound must have
been formed from Cu+, S2-. The name of the is Copper(I)
sulfide.
d.
SnO
Since neither of the elements have a subscript, you know
that the positive ion must be equal in value to the negative
ion. Since you know that the oxide ion has a charge of -2,
the tin ion must have a charge of +2. The compound must
have been formed from Sn2+, O2-. The name of the
compound is Tin(II) oxide.
You Try It
1.
Circle the compounds below that would need a Roman numeral when naming them.
CuCl2
Fe2O3
BaCl2
LiF
MgS
CaO
SrF2
CoI3
7
2.
Write names for the following binary ionic compounds. (Do not use prefixes!)
Remember to use a Roman numeral when appropriate.
a.
Li2S
b.
FeS
c.
ZnI2
d.
NaBr
e.
CuO
f.
HgS
g.
CaO
h.
MgS
i.
K2O
j.
PbO2
Naming and Writing Formulas for Ternary Ionic Compounds
Ternary ionic compounds contain one or more polyatomic ions.
To name a ternary ionic compound, you name the cation followed by the anion.
Then ending of a polyatomic ion should never be changed.
Ex.
Li2SO4
Ba(NO2)2
FeCO3
Lithium sulfate
Barium nitrite
Iron(II) carbonate
(Since CO3 has a -2 charge, the Fe
must be +2.)
To write the formulas for ternary ionic compounds, you do the same thing you did when
writing the formulas for binary ionic compounds. The only difference is that you must
sometimes use parentheses. Parentheses are used to indicate that you need more than one
of a polyatomic ion.
Ex.
Barium chlorite
Calcium sulfate
Ammonium nitrate
Copper(II) phosphate
Ba2+, ClO2Ca2+, SO42NH4+, NO3Cu2+, PO43-
Ba(ClO2)2
CaSO4
NH4NO3
Cu3(PO4)2
8
You Try It
1.
Name the following ionic compounds. Remember to use Roman numerals when
appropriate. The first one has been done as an example.
2.
a.
Li2SO3
b.
CaCO3
c.
NH4Cl
d.
FeSO4
e.
Ba(ClO3)2
f.
CuSO4
g.
SnCl2
h.
Cu3PO4
i.
K2Cr2O7
j.
AgC2H3O2
k.
ZnSO3
Lithium sulfite
Write the chemical formula for the following ionic compounds. Hint: First
determine the symbols for the ions involved. The first one has been done as an
example.
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
Sodium nitrate
Barium sulfide
Copper(II) carbonate
Lithium perchlorate
Tin(IV) oxalate
Iron(III) sulfide
Ammonium bromide
Potassium phosphate
Copper(I) nitride
Magnesium phosphide
Magnesium phosphate
Na+, NO3-
9
NaNO3
Naming and Writing Formulas for Acids and Bases
Text Reference: 454-455
Acids
Acids are compounds that produce hydrogen ions (H+) in water. If a compound has an H
listed as the first element, we will name it as an acid.
Naming and Writing Formulas for Binary Acids
Binary acids are composed of two elements: hydrogen and a nonmetal. The name is
composed of the prefix hydro-, stem and suffix of –ic. Here are a few examples.
HCl
HBr
H 2S
Hydrochloric acid
Hydrobromic acid
Hydrosulfuric acid
Writing the formulas for binary acids is easy. You simply write down the symbols for the
ions involved and balance the charges. Here are a few examples.
Hydroiodic acid
Hydroselenic acid
H+, IH+, Se2-
HI
H2Se
Naming and Writing Formulas for Oxyacids
Oxyacids are composed of hydrogen and a polyatomic ion that contains oxygen.
The name for the most common form of a polyatomic ion ends in –ate. When naming the
acids containing the polyatomic ion –ate, you simply replace the –ate ending with –ic acid.
DO NOT USE THE PREFIX HYDRO. Here are some examples:
ClO3NO3SO42PO43-
chlorate
nitrate
sulfate
phosphate
HClO3
HNO3
H2SO4
H3PO4
chloric acid
nitric acid
sulfuric acid
phosphoric acid
What about the names of acids containing the other forms of the polyatomic ions? The
polyatomic ion making up the acid is compared to the most common form of the polyatomic
ion in terms of number of oxygen atoms. Prefixes and suffixes are used to name them.
Let’s look at an example using the acids of chlorine.
ClO3ClO4ClO2ClO-
chlorate
most common form of the polyatomic ion
perchlorate one more oxygen than the -ate form
chlorite
one less oxygen than the –ate form
hypochlorite two less oxygens than the –ate form
10
HClO3
HClO4
HClO2
HClO
chloric acid
perchloric acid
chlorous acid
hypochlorous acid
Here are the steps you need to take to write the names for oxyacids.
1.
First determine the symbol for the polyatomic ion making up the acid.
2.
Determine the name of the polyatomic ion. If the polyatomic ion is not on the list
you were given, find the most common form of the polyatomic ion (-ate form). How
does the polyatomic ion on the list compare to the one in the acid?
One more oxygen
per
ate polyatomic ion
One less oxygen
-ite polyatomic ion
Two less oxygens
hypo
ite polyatomic ion
3.
Add the appropriate prefixes and suffixes.
-ate
-ic acid
Per
ate
per
ic acid
-ite
-ous acid
Hypo
ite
hypo
ous acid
Example 1: HBrO3
1.
What is the symbol for the polyatomic ion making up the acid?
Ans. BrO32.
What is the name of the polyatomic ion?
Ans. This happens to be the form given on the list of the polyatomic ions. The name
of the ion is bromate.
3.
What is the name of the acid?
Ans. Since it is the –ate form of the polyatomic ion, the acid is bromic acid.
Example 2: H2CO2
1.
What is the symbol for the polyatomic ion making up the acid?
Ans. CO222.
What is the name of the polyatomic ion?
Ans. This form of the polyatomic ion is not on the list. However, CO32- is on the list
as carbonate. Since this form has one less oxygen it must be carbonite.
3.
What is the name of the acid?
Ans. Since it is the –ite form of the polyatomic ion, the acid is carbonous acid.
Example 3: H2SO3
1.
What is the symbol for the polyatomic ion making up the acid?
Ans. SO322.
What is the name of the polyatomic ion?
Ans. This happens to be one of the forms given on the list of the polyatomic ions.
The name of the ion is sulfite.
3.
What is the name of the acid?
Ans. Since it is the –ite form of the polyatomic ion, the acid is sulfurous acid.
11
Writing the Formulas for Oxyacids
In order to write formulas for the oxyacids, you must first identify the symbols of the
ions involved. Then you balance the charges. Here are a few examples.
Example 1: Phosphoric acid
Since the name ends in –ic, you know it came from the phosphate polyatomic ion. What is
the symbol for the phosphate polyatomic ion? Answer: PO43The ions involved are H+, PO43-. Therefore the formula for phosphoric acid is H3PO4.
Example 2: Oxalous acid
Since the name ends in –ous, you know it came from the oxalite polyatomic ion. What is
the symbol for oxalite polyatomic ion? The closest thing to oxalite on the polyatomic ions
list is oxalate, C2O42-. Oxalite will have one less oxygen. Therefore the symbol for oxalite
is C2O32-.
The ions involved are H+, C2O32-. Therefore the formula for oxalous acid is H2C2O3.
Example 3: Periodic acid (pronounced like purr-iodic and not periodic like the table)
Since the polyatomic ion has per at the front, you know it came from the periodate
polyatomic ion. What is the symbol for the periodate polyatomic ion? The closest thing to
periodate ion the polyatomic ions list is iodate, IO3-. Periodate will have one more oxygen.
Therefore the symbol for periodate is IO4-.
The ions involved are H+, IO4-. Therefore the formula for periodic acid is HIO4.
You Try It
1.
Name the following acids. Caution: Some of them are binary acids and some of
them are oxyacids.
2.
a.
HF
b.
HIO
c.
H2CO3
d.
HBrO2
e.
HI
Write formulas for the following acids. Caution: Some of them are binary acids and
some of them are oxyacids.
a.
Perbromic acid
b.
Acetic acid
c.
Hydrosulfuric acid
d.
Phosphorous acid
12
Bases
Bases are compounds that produce hydroxide ions (OH-) in water.
Naming Bases
Bases are very easy to name. They are named by naming the metallic ion (cation) followed
by the word hydroxide. Here are a few examples.
Roman numerals are used when the metallic
LiOH
Lithium hydroxide
ion has more than one common oxidation
Mg(OH)2
Magnesium hydroxide
number.
Cu(OH)2
Copper(II) hydroxide
Note: NH3 is a common base known as ammonia. You need to memorize the formula for
ammonia.
Writing Formulas for Bases
The same procedure for writing the formulas for bases is used as the one you learned for
ionic compounds. You first identify the symbols of the ions involved and then you balance
the charges. Here are a few examples.
Potassium hydroxide
Iron(III) hydroxide
Calcium hydroxide
K+, OHFe3+, OHCa2+, OH-
KOH
Fe(OH)3
Ca(OH)2
You Try It
1.
Name the following bases.
2.
a.
NaOH
b.
Sr(OH)2
c.
Pb(OH)4
d.
Al(OH)3
e.
Cr(OH)3
Write chemical formulas for the following bases. Hint: Write the symbols for the
ions involved first.
a.
Barium hydroxide
b.
Iron(II) hydroxide
c.
Zinc hydroxide
d.
Rubidium hydroxide
e.
Tin(IV) hydroxide
13