General, Organic, and Biological
Chemistry
Chapter Three
Ionic Compounds
Vitamin Story…
Why do atoms bond together to form
compounds?
• Valence electrons: e- in the outermost
PEL of an atom or ion.
• All chemical activity involves the electrons
in the outermost PEL.
• Ex. Consider group 1 elements:
Li (1s2 2s1) has 1 val. e-.
Na (1s2 2s2 2p6 3s1) has 1 val. e-.
K ([Ar] 4s1) has 1 val. e-.
*All elements in group 1 have 1 val. e-.
All elements within a group have similar
chemical properties because they have
the same # of val. e-.
•
•
•
•
Group 2 elements all have 2 val. e-.
Group 13 elements – 3 val. e-.
Group 17 elements – 7 val. e-.
Group 18 elements – 8 val. e-.
*Exception: He only has 2 val. e-.
No element can have more than 8 val. e-.
• 8 valence e- is considered a full valence
shell.
• He only has one PEL, so its val. shell is
filled with 2 val. e-.
• Noble gases (group 18) are relatively very
stable (unreactive) because they all have
a full valence shell.
• Atoms will gain, lose, or share valence
e- in order to obtain a noble gas econfig. Usually, this is 8 val. e-, or a
“stable octet of valence e-.”
Lewis electron dot diagrams show the
valence electrons in an atom only.
• Step 1: Draw the chemical symbol of
the element. This represents the
atom’s “kernel”: the nucleus and all
electrons except the valence shell.
Ex. Li
• Use dots to represent the valence e-.
Ex. Li ·
Exercise
e- dot diagrams for all period 2 and 3
elements.
Ion: A charged particle due to the
gain or loss of valence electrons.
Na atom
Q: How many p+, no, and e- does an atom of Na
have?
Ion: A charged particle due to the
gain or loss of valence electrons.
11 p+
12 no
Na atom
Q: What is the simple e- config. for Na?
Ion: A charged particle due to the
gain or loss of valence electrons.
11 p+
12 no
2e- 8e- 1e-
Na atom
Q: How many val. e- does Na want? How can
this happen?
Ion: A charged particle due to the
gain or loss of valence electrons.
11 p+
12 no
Lose 1 val. e2e- 8e- 1e-
11 p+
12 no
2e- 8e-
+ 1e-
Na atom
Na+ ion
Q: What are the charges in the new Na ion?
Ion: A charged particle due to the
gain or loss of valence electrons.
11 p+
12 no
Lose 1 val. e2e- 8e- 1e-
11 p+
12 no
2e- 8e-
+ 1e-
Na+ ion
11 p+
Q: What is the new e- config.
10 eof the Na+ ion?
+ 1 charge
Na atom
Ion: A charged particle due to the
gain or loss of valence electrons.
11 p+
12 no
Lose 1 val. e2e- 8e- 1e-
11 p+
12 no
2e- 8e-
+ 1e-
Na+ ion
11 p+
10 e+ 1 charge
(Na+ has the same e- config as Ne, a noble gas)
Na atom
This process can be shown more easily
with e- dot diagrams:
Na ·
[Na]+ + 1e-
This is the equation for the formation of an
ion from a parent metal atom.
How does Ca form a Ca2+ ion?
This process can be show more easily
with e- dot diagrams:
Na ·
[Na]+ + 1e-
How does Ca form a Ca2+ ion?
Ca:
[Ca]2+ + 2e-
Metals tend to form (+) charged ions
(cations) by losing valence e-.
Metals tend to form (+) charged ions
(cations) by losing valence e-.
• Cations tend to assume noble gas econfigs.
Q: How does the size of a cation compare
to that of the parent atom?
Ion: A charged particle due to the
gain or loss of valence electrons.
11 p+
12 no
Lose 1 val. e2e- 8e- 1e-
11 p+
12 no
2e- 8e-
+ 1e-
Na+ ion
11 p+
10 e+ 1 charge
(Na+ has the same e- config as Ne, a noble gas)
Na atom
Metals tend to form (+) charged ions
(cations) by losing valence e-.
• Cations tend to assume noble gas econfigs.
• Cations are smaller than their parent
atoms (greater (+) to (-) charge ratio)
Q: How many val. e- do group 1 elements
have? What kind of ions to they form?
Metals tend to form (+) charged ions
(cations) by losing valence e-.
• Cations tend to assume noble gas econfigs.
• Cations are smaller than their parent
atoms (greater (+) to (-) charge ratio)
• Group 1 elements lose their 1 val. e- to
form 1+ ions.
Q: How many val. e- do group 2 elements
have? What kind of ions to they form?
Metals tend to form (+) charged ions
(cations) by losing valence e-.
• Cations tend to assume noble gas econfigs.
• Cations are smaller than their parent
atoms (greater (+) to (-) charge ratio)
• Group 1 elements lose their 1 val. e- to
form 1+ ions.
• Group 2 elements lose their 2 val. e- to
form 2+ ions.
Naming Cations
• To name a cation, use the metal’s name
followed by the word “ion.”
Ex. Na+ = sodium ion
Mg2+ = magnesium ion
Q: What kind of ions do you suppose
nonmetal atoms tend to form?
Nonmetals tend to form (-) charged
ions (anions)
Q: How do you suppose nonmetals form (-)
charged ions?
Nonmetals tend to form (-) charged
ions (anions) by gaining val. e-.
Q: Consider F. How many p+, no, and edoes an atom of F contain?
Nonmetals tend to form (-) charged
ions (anions) by gaining val. e-.
9 p+
10 no
F atom
Q: What is the simple e- config for F?
Nonmetals tend to form (-) charged
ions (anions) by gaining val. e-.
9 p+
10 no
2e-
7e-
F atom
Q: How many e- must F gain to be happy?
Nonmetals tend to form (-) charged
ions (anions) by gaining val. e-.
9 p+
10 no
2e-
7e-
F atom
+ 1 e-
9 p+
10 no
2e- 8e-
F- ion
Q: What are the charges in the new F- ion?
Nonmetals tend to form (-) charged
ions (anions) by gaining val. e-.
9 p+
10 no
2e-
7e-
F atom
+ 1 e-
9 p+
10 no
F- ion
Q: Which element normally has an
e- config. of 2-8?
2e- 8e-
9 p+
10 e-1 charge
Nonmetals tend to form (-) charged
ions (anions) by gaining val. e-.
9 p+
10 no
2e-
7e-
+ 1 e-
9 p+
10 no
9 p+
10 e-1 charge
Isoelectric (same e- config.) as Na+, Ne
F atom
F- ion
2e- 8e-
This process can be show more easily
with e- dot diagrams:
..
:F: + 1e·
..
:F: ··
This is the equation for the formation of an
ion from a parent nonmetal atom.
Show the formation of an oxygen ion from
an oxygen atom.
Q: How do you suppose the size of an
anion compares to that of its parent atom?
9 p+
10 no
2e-
7e-
F atom
+ 1 e-
9 p+
10 no
F- ion
2e- 8e-
Anions
• Anions tend to be larger than their parent
atoms (lower (+) to (-) charge ratio).
Q: How many valence e- do group 17
element have? What kind of ions to they
form?
Anions
• Anions tend to be larger than their parent
atoms (lower (+) to (-) charge ratio).
• Group 17 elements tend to gain 1 val. e- to
form 1- ions.
Q: How many valence e- do group 16
element have? What kind of ions to they
form?
Anions
• Anions tend to be larger than their parent
atoms (lower (+) to (-) charge ratio).
• Group 17 elements tend to gain 1 val. e- to
form 1- ions.
• Group 16 elements tend to gain 2 val. e- to
form 2- ions.
Anions
• Anions tend to be larger than their parent
atoms (lower (+) to (-) charge ratio).
• Group 17 elements tend to gain 1 val. e- to
form 1- ions.
• Group 16 elements tend to gain 2 val. e- to
form 2- ions.
• To name an anion, replace the ending of
the element with the suffix “-ide” followed
by the word “ion”.
Ex. F- = fluoride ion
S2- = sulfide ion
Q: What do you suppose would happen if a
Na+ ion and a F- ion approached each other?
Q: What do you suppose would happen if a
Na+ ion and a F- ion approached each other?
• Ionic Bond: A force of attraction between
two oppositely charged ions.
Ex. Na+ F- (or NaF), an ionic compound.
• An ionic bond can be formed by the
transfer of one or more electrons.
• An ionic compound is a compound that
contains ionic bonds.
Formation of an Ionic Bond
Example:
..
Na . + . Cl:
..
..
[Na]+ :Cl:
..
An electron is transferred from the sodium
atom to the chlorine atom to form positive
and negative ions.
3.4 Some Properties of Ionic
Compounds
• Ionic compounds are usually crystalline
solids.
Copper (II) sulfate pentahydrate
crystals
3.4 Some Properties of Ionic
Compounds
• Ionic compounds are usually crystalline
solids.
• Ions in an ionic solid are held rigidly in
place by attraction to their neighbors and
cannot move about.
• Once an ionic solid is dissolved in water or
melted, the ions can move freely and
conduct electricity.
3.4 Some Properties of Ionic
Compounds
• High melting points and boiling points are
observed for ionic compounds because the
attractive forces are extremely strong.
• Sodium chloride melts at 801ºC and boils at
1413ºC.
• Ionic solids are not malleable and will shatter
if struck sharply.
• Ionic compounds dissolve in water if the
attraction between water and the ions
overcomes the attraction of the ions for one
another.
3.4 Some Properties of Ionic
Compounds
• Sodium chloride and some other familiar
ionic compounds are very soluble and can
be dissolved to make solutions of high
concentration.
• Other ionic compounds are not watersoluble, because water is unable to
overcome the ionic forces in many
crystals.
Ionic Charges
• Main group element tend to form only one
kind of charge.
• Examples: ________________________
• Many transition metals can form more than
one kind of ion. Transition metal ions tend
to form colored aqueous solutions.
• Ions of transition metals are named by
placing their charges in Roman numerals
inside parentheses after the metal’s name.
Ex. Fe2+ = Iron (II)
Fe3+ = Iron (III)
Potassium dichromate
(contains Cr2O72- ions)
Copper (II) sulfate
(contains Cu2+ ions)
Potassium permanganate
(contains MnO4- ions)
Nickel (II) chloride
(contains Ni2+ ions)
Old Latin suffixes used to be used to denote an ion’s
charge: “-ous” indicated the lower charge, “-ic” indicated
the larger charge.
Table 3.1
Polyatomic ions:
• A group of atoms or ions that behave
as a single ion. When more than one
“radical” is present, use parentheses
and subscripts.
• See polyatomic ions list on next slide.
• Name:
SO42- __________________
OH- ___________________
Make flash cards to memorize these!!!
Polyatomic ions:
Table 3.3
Formula Writing
•
•
•
Binary compounds: Compounds that
contain exactly two elements.
To write the formulas for binary compounds,
the charges must be balanced. We can
do this by using the criss-cross method:
Step 1: Write the chemical symbols.
The more positive symbol is written first.
Ex. Al O
• Step 1: Write the chemical symbols. The
more positive symbol is written first.
Ex. Al O
• Step 2: Write the most common oxidation
state (charge) above each element.
+3
-2
Ex. Al
O
• Step 3: Criss-cross the charges. Drop the
signs and use the #s as subscripts.
+3
Ex. Al
-2
O
=
Al2O3
Step 3: Criss-cross the charges. Drop the
signs and use the #s as subscripts.
+3
-2
Ex. Al
O
=
Al2O3
• Name this compound:
_________________________
Practice
Write the chemical formulas for
compounds containing:
1. Ca and Cl
2. Al and F
3. K and S
FYI: Since polyatomic ions are to be treated
as a single ion, the criss-cross method works
perfectly for these ions too.
*If a polyatomic ion is used:
• Use parentheses around the ion if more
than one is present.
• Use the charge of the ion in step 2.
• Ex. calcium nitrate
Ca
NO3
Ex. calcium nitrate
Ca
NO3
2+
1-
Ca
NO3
2+
1-
Ca
NO3
Ca(NO3)2
Practice
Write the formulas for:
1. Sodium hydroxide
2. Calcium phosphate
Interpreting formulas
Consider Ca3(PO4)2
How many of each atom/ion is represented:
Ca: ___________atoms
P: ___________ atoms
O: ___________ atoms
Total:
Troublemakers: the transition metals
• If a metal can form more than one kind
of ion, the charge must be denoted with
Roman numerals in parentheses after
the metal’s name.
Ex. Iron (II) = Fe2+
Iron (III) = Fe3+
Copper (II) chloride:
Copper (I) chloride:
Troublemakers: the transition metals
• If a metal can form more than one kind
of ion, the charge must be denoted with
Roman numerals in parentheses after
the metal’s name.
Ex. Iron (II) = Fe2+
Iron (III) = Fe3+
Copper (II) chloride: CuCl2
Copper (I) chloride: CuCl
Copper (I) chloride
(cuprous chloride)
CuCl
Copper (II) chloride
(cupric chloride)
CuCl2
Practice
Write the formula for calcium oxide.
Ca2O2
Problem: ionic compounds exist as crystals…
Ca2O2 : a crystal
Ionic compounds are expressed using an
empirical formula.
Ionic compounds are expressed using an
empirical formula.
• Empirical formula: The simplest, whole #
ratio of atoms in a compound; used to
represent compounds that exist as
crystals, rather than molecules. Use the
empirical formula for compounds
composed of metal-nonmetal combinations
or if a polyatomic ion is present.
• Ca2O2 becomes CaO
Naming ionic compounds
• Name the cation followed by the name
of the anion.
Ex. NaCl = sodium chloride
CaF2 = calcium fluoride
*Polyatomic ions – if a polyatomic ion
is present, use the name of the ion
when naming the compound.
Ex. CaSO4
Naming ionic compounds
*If an element (metal) can form more than
one kind of charge, the charge used is
written in Roman numerals after the
element’s name.
Ex. Fe2O3
Ex. FeO
Naming ionic compounds
+3
-2
Ex. Fe2O3
= Iron (III) oxide
+6 -6 = 0
________________________________________________________
+2 -2
Ex. FeO
= Iron (II) oxide
+2 -2 = 0
All charges must add up to zero!!!
Crystal
Crystal Structures
Structures of
of Iron
Iron Oxides
Oxides
Iron (II) oxide, FeO
crystal structure
Iron (III) oxide, Fe2O3
crystal structure
Table 3.4
3.11 H+ and OH- Ions: An Introduction
to Acids and Bases
• The importance of the H+ cation and the
OH- anion is that they are fundamental to
the concepts of acids and bases.
• Acid: A substance that produces H+ ions
when dissolved in water; for example,
Example: HCl  H+ + Cl• Base: A substance that provides OH- ions
in water; for example,
Example: NaOH  Na+ + OH-
Common Acids (page 93)
Table 3.5
Nomenclature Worksheet
nitrate
sulfate
sodium
NaNO3
Na2SO4
·
·
·
·
silver
·
·
·
·
·
·
ammonium
·
·
·
·
·
·
OMIT
OMIT
OMIT
OMIT
OMIT
OMIT
OMIT
zinc
·
·
·
·
·
·
calcium
carbonate phosphate hydroxide chromate
Nomenclature Worksheet Answers
nitrate
sulfate
carbonate
phosphate
hydroxide
chromate
sodium
NaNO3
Na2SO4
Na2CO3
Na3PO4
NaOH
Na2CrO4
silver
AgNO3
Ag2SO4
Ag2CO3
Ag3PO4
AgOH
Ag2CrO4
ammonium
NH4NO3
(NH4)3PO4
NH4OH
(NH4)2CrO4
OMIT
OMIT
OMIT
OMIT
OMIT
OMIT
OMIT
zinc
Zn(NO3)2
ZnSO4
ZnCO3
Zn3(PO4)2
Zn(OH)2
ZnCrO4
calcium
Ca(NO3)2
CaSO4
CaCO3
Ca3(PO4)2
Ca(OH)2
CaCrO4
(NH4)2SO4 (NH4)2CO3
Chapter Summary
•
•
•
Atoms are converted into cations by the loss of one or
more electrons and into anions by the gain of one or
more electrons.
Ionic compounds are composed of cations and anions
held together by ionic bonds. Ionic compounds conduct
electricity when dissolved in water, and they are
generally crystalline solids with high melting points and
high boiling points.
Main group elements tend to form ions in which they
have gained or lost the appropriate number of electrons
to reach a noble gas configuration.
Chapter Summary Contd.
•
•
•
•
Metals lose electrons more easily than nonmetals. As a
result, metals usually form cations.
Nonmetals gain electrons more easily than metals. As
a result, reactive nonmetals usually form anions.
The ionic charge can be predicted from the group
number and the octet rule. For main group metals, the
charge on the cation is equal to the group number. For
nonmetals, the charge on the anion is equal to the
group number-8.
Ionic compounds contain appropriate numbers of
anions and cations to maintain overall neutrality.
Chapter Summary Contd.
•
•
•
•
Cations have the same name as the metal, monatomic
anions have the name ending -ide.
For metals that form more than one ion, a Roman
numeral equal to the charge is used to name the ion.
The cation name is given first, with the charge of the
metal ion indicated if necessary, and the anion name is
given second.
An acid is a substance that yields H+ ions when
dissolved in water, and a base is a substance that
yields OH- ions when dissolved in water.
Key Words
•Acid
•Anion
•Base
•Cation
•Electron affinity
•Formula unit
•Ion
•Ionic bond
•Ionic compound
•Ionic solid
•Ionization energy
•Octet rule
•Polyatomic ion