The document discusses ionic bonds and ionic compounds. It explains that ionic compounds form when oppositely charged ions attract via electrostatic forces called ionic bonds. Ionic compounds are crystalline solids that are electrically neutral, have high melting points, and can conduct electricity when molten or dissolved in water as the ions are free to move. Sodium chloride is given as a common example of an ionic compound composed of sodium and chloride ions.

1. 7.2 Ionic Bonds and Ionic Compounds >
Chapter 7
Ionic and Metallic Bonding
7.1 Ions
7.2 Ionic Bonds and
Ionic Compounds
7.3 Bonding in Metals
1
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2. 7.2 Ionic Bonds and Ionic Compounds >
CHEMISTRY & YOU
Where does table salt come from?
In some countries,
salt is obtained by
the evaporation of
seawater. In other
countries, salt is
mined from rock
deposits deep
underground.
2
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3. 7.2 Ionic Bonds and Ionic Compounds > Formation of Ionic
Compounds
Formation of Ionic Compounds
What is the electrical charge of an
ionic compound?
3
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4. 7.2 Ionic Bonds and Ionic Compounds > Formation of Ionic
Compounds
Sodium chloride, or table salt, is an ionic
compound consisting of sodium cations
and chloride anions.
• An ionic compound is a compound
composed of cations and anions.
4
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5. 7.2 Ionic Bonds and Ionic Compounds > Formation of Ionic
Compounds
Although they are composed of
ions, ionic compounds are
electrically neutral.
• The total positive charge of the
cations equals the total negative
charge of the anions.
5
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6. 7.2 Ionic Bonds and Ionic Compounds > Formation of Ionic
Compounds
Ionic Bonds
Anions and cations have opposite charges
and attract one another by means of
electrostatic forces.
• The electrostatic forces that hold ions
together in ionic compounds are called
ionic bonds.
6
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7. 7.2 Ionic Bonds and Ionic Compounds > Formation of Ionic
Compounds
Ionic Bonds
When sodium and chlorine react to form a
compound, the sodium atom transfers its one
valence electron to the chlorine atom.
• Sodium and chlorine atoms combine in a one-toone ratio, and both ions have stable octets.
7
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8. 7.2 Ionic Bonds and Ionic Compounds > Formation of Ionic
Compounds
Ionic Bonds
Aluminum metal (Al) and
the nonmetal bromine (Br2)
react violently to form the
ionic solid aluminum
bromide (AlBr3).
• Each bromine atom has seven
valence electrons and readily
gains one additional electron.
• Three bromine atoms
combine with each aluminum
atom.
8
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9. 7.2 Ionic Bonds and Ionic Compounds > Formation of Ionic
Compounds
Formula Units
A chemical formula shows the
numbers of atoms of each element in
the smallest representative unit of a
substance.
• NaCl is the chemical formula for sodium
chloride.
9
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10. 7.2 Ionic Bonds and Ionic Compounds > Formation of Ionic
Compounds
Formula Units
Ionic compounds do not exist as discrete units, but as
collections of positively and negatively charged ions
arranged in repeating patterns.
10
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11. 7.2 Ionic Bonds and Ionic Compounds > Formation of Ionic
Compounds
Formula Units
The chemical formula of an ionic
compound refers to a ratio known as a
formula unit.
• A formula unit is the lowest wholenumber ratio of ions in an ionic compound.
11
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12. 7.2 Ionic Bonds and Ionic Compounds > Formation of Ionic
Compounds
Formula Units
For sodium chloride, the lowest wholenumber ratio of the ions is 1:1 (one
Na+ ion to each Cl– ion).
• The formula unit for sodium chloride is NaCl.
• Although ionic charges are used to derive the
correct formula, they are not shown when
you write the formula unit of the compound.
12
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13. 7.2 Ionic Bonds and Ionic Compounds >
Sample Problem 7.1
Predicting Formulas of Ionic Compounds
Use electron dot structures to
predict the formulas of the ionic
compounds formed from the
following elements:
a. potassium and oxygen
b. magnesium and nitrogen
13
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14. 7.2 Ionic Bonds and Ionic Compounds >
Sample Problem 7.1
1 Analyze Identify the relevant concepts.
• Atoms of metals lose valence electrons
when forming an ionic compound.
• Atoms of nonmetals gain electrons.
• Enough atoms of each element must be
used in the formula so that electrons lost
equal electrons gained.
14
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15. 7.2 Ionic Bonds and Ionic Compounds >
Sample Problem 7.1
2 Solve Apply the concepts to this problem.
a. Start with the atoms.
••
••
• and • O
K
•
15
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16. 7.2 Ionic Bonds and Ionic Compounds >
Sample Problem 7.1
2 Solve Apply the concepts to this problem.
a. In order to have a completely filled valence
shell, the oxygen atom must gain two
electrons. These electrons come from two
potassium atoms, each of which loses one
electron.
K•
K+
••
O
••
2–
••
••
16
••
K•
+
••
•O
•
K+
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17. 7.2 Ionic Bonds and Ionic Compounds >
Sample Problem 7.1
2 Solve Apply the concepts to this problem.
a. Express the electron dot structure as a
formula.
• The formula of the compound formed is
K2O (potassium oxide).
17
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18. 7.2 Ionic Bonds and Ionic Compounds >
Sample Problem 7.1
2 Solve Apply the concepts to this problem.
b. Start with the atoms.
•
•
•
18
••
Mg and • N
•
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19. 7.2 Ionic Bonds and Ionic Compounds >
Sample Problem 7.1
2 Solve Apply the concepts to this problem.
b. Each nitrogen atom needs three electrons
to have an octet, but each magnesium
atom can lose only two electrons. Three
magnesium atoms are needed for every
two nitrogen atoms.
•
•
Mg
•
19
•N
•
Mg2+
••
N
••
3–
••
N
••
3–
••
••
Mg
•
••
•
•
+
•N
•
Mg2+
••
••
•
•
••
Mg
Mg2+
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20. 7.2 Ionic Bonds and Ionic Compounds >
Sample Problem 7.1
2 Solve Apply the concepts to this problem.
b. Express the electron dot structure as a
formula.
• The formula of the compound formed is
Mg3N2 (magnesium nitride).
20
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21. 7.2 Ionic Bonds and Ionic Compounds >
Use electron dot structures to
determine the formula of the ionic
compound formed when calcium
reacts with fluorine.
21
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22. 7.2 Ionic Bonds and Ionic Compounds >
Use electron dot structures to
determine the formula of the ionic
compound formed when calcium
reacts with fluorine.
•
Ca
–
Ca2+
••
F
••
–
••
••
••
F
•
••
••
•
+
••
F
••
••
••
••
••
••
F
•
CaF2
22
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23. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
Properties of Ionic Compounds
What are three properties of
ionic compounds?
23
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24. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
Most ionic compounds are crystalline
solids at room temperature.
• The component ions in such crystals
are arranged in repeating threedimensional patterns.
The beauty of
crystalline solids
comes from the
orderly arrangement of
their component ions.
24
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25. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
Each ion is attracted strongly to each of its
neighbors, and repulsions are minimized.
• The large attractive forces result in a very
stable structure.
25
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26. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
Ionic compounds generally have
high melting points.
26
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27. 7.2 Ionic Bonds and Ionic Compounds >
CHEMISTRY & YOU
Would you expect to find sodium
chloride in underground rock deposits
as a solid, liquid, or gas? Explain.
27
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28. 7.2 Ionic Bonds and Ionic Compounds >
CHEMISTRY & YOU
Would you expect to find sodium
chloride in underground rock deposits
as a solid, liquid, or gas? Explain.
Sodium chloride is found in
underground rock deposits
as a solid. Like most ionic
compounds, sodium
chloride has a high melting
point (about 800°C).
28
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29. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
The coordination number of an ion is the
number of ions of opposite charge that
surround the ion in a crystal.
• In NaCl, each ion has a
coordination number of 6.
– The coordination number of
Na+ is 6 because each Na+ ion
is surrounded by six Cl– ions.
– The coordination number of Cl–
is also 6 because each Cl– ion
is surrounded by six Na+ ions.
29
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30. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
In CsCl, each ion has a coordination
number of 8.
• Each Cs+ ion is
surrounded by
eight Cl– ions.
• Each Cl– ion is
surrounded by
eight Cs+ ions.
30
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31. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
Titanium dioxide (TiO2), or rutile,
forms tetragonal crystals.
• The coordination
number for the cation
(Ti4+) is 6.
– Each Ti4+ ion is surrounded
by six O2– ions.
• The coordination number
of the anion (O2–) is 3.
– Each O2– ion is surrounded by
three Ti4+ ions.
31
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32. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
Ionic compounds can conduct an
electric current when melted or
dissolved in water.
32
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33. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
When sodium chloride is melted, the orderly
crystal structure breaks down.
Power source
• If a voltage is
applied across
this molten
mass, cations
migrate freely
to one
electrode and
anions migrate
to the other.
Current meter
Flow of
electrons
Inert metal
electrodes
Flow of
electrons
Cl–
Na+
To (+)
electrode
To (–)
electrode
• This movement of electrons allows electric current to
flow between the electrodes through an external wire.
33
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34. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
This solar facility uses molten NaCl for its ability
to absorb and hold a large quantity of heat,
which is used to generate electricity.
34
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35. 7.2 Ionic Bonds and Ionic Compounds > Properties of Ionic
Compounds
Ionic compounds also conduct electric
current if they are dissolved in water.
• When dissolved, the ions are free to move
about in the solution.
35
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36. 7.2 Ionic Bonds and Ionic Compounds >
When can ionic compounds conduct
an electric current?
A. Only when melted
B. When melted or dissolved in water
C. Only when dissolved in water
D. When solid or melted
36
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37. 7.2 Ionic Bonds and Ionic Compounds >
When can ionic compounds conduct
an electric current?
A. Only when melted
B. When melted or dissolved in water
C. Only when dissolved in water
D. When solid or melted
37
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38. 7.2 Ionic Bonds and Ionic Compounds > Key Concepts
Although they are composed of ions, ionic
compounds are electrically neutral.
Most ionic compounds are crystalline
solids at room temperature.
Ionic compounds generally have high
melting points.
Ionic compounds can conduct an electric
current when melted or dissolved in water.
38
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39. 7.2 Ionic Bonds and Ionic Compounds > Glossary Terms
• ionic compound: a compound composed of
positive and negative ions
• ionic bond: the electrostatic attraction that
binds oppositely charged ions together
• chemical formula: an expression that
indicates the number and type of atoms
present in the smallest representative unit of a
substance
39
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40. 7.2 Ionic Bonds and Ionic Compounds > Glossary Terms
• formula unit: the lowest whole-number ratio
of ions in an ionic compound; in magnesium
chloride, the ratio of magnesium ions to
chloride ions is 1:2 and the formula unit is
MgCl2
• coordination number: the number of ions of
opposite charge that surround each ion in a
crystal
40
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41. 7.2 Ionic Bonds and Ionic Compounds > BIG IDEA
Bonding and Interactions
• The electrostatic forces between the
oppositely charged ions hold the
cations and anions together in an ionic
compound.
• Ionic compounds generally have high
melting points and can conduct an
electric current in solution and in the
molten state.
41
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42. 7.2 Ionic Bonds and Ionic Compounds >
END OF 7.2
42
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