Ionic Bonding & Ionic
Compounds
Objectives
Explain how ionic compounds are formed
 Explain the electrical charge of an ionic
compound
 Describe three properties of ionic
compounds

Important Vocabulary
 Ionic
compounds
 Ionic bonds
 Chemical formula
 Formula unit
 Coordination number
Formation of Ionic
Compounds
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Compounds composed of cations and anions are
called ionic compounds
They usually are the combination of a metal
cation with a non-metal anion
For example: sodium chloride
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
Ionic Bonds
Opposite charges attract
 This attraction causes cations and anions
to bind together forming an ionic bond
 An ionic bond is a chemical bond formed
between two ions of opposite charges

Formation of an Ionic
Bond
Formula Units
Chemists represent the composition of
substances by writing chemical formulas
 A chemical formulas shows the kinds
and numbers of atoms in the smallest
representative unit of a substance
 A formula unit is the lowest wholenumber ratio of ions in an ionic compound

Formula Units Example
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NaCl
 is 1 sodium ion & 1 chloride ion
 The whole-number ratio is 1:1
MgCl2
 is 1 magnesium ion & 2 chloride ions
 The whole-number ratio is 1:2
Why?
Practice Problems

1.
Use electron dot structures to predict the
formulas of the ionic compounds formed from
the following elements
Potassium and oxygen
2.
Magnesium and nitrogen
3.
Sodium and bromine
4.
Aluminum and oxygen
Properties of Ionic
Compounds
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Most are crystalline solids at room
temperature
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The component ions within these crystals are
arranged in repeating 3-D patterns
The coordination number of an ion is the number of
ions of opposite charge that surround the ion in a
crystal
They usually have high melting points and
boiling points
They also can conduct electricity when
dissolved in water or melted
Ionic Compound Crystals
Ionic Compound Crystals
Coordination
Number
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In sodium chloride, (NaCl)
Na+ ion has a coordination
number of 6 because each
one is surrounded by 6 Clions
In titanium (IV) oxide,
(TiO2) the coordination
number for O2- ion is 3
because it is surrounded by 3
Ti4+ ions
Conduction of Electricity

Why can dissolved or melted ionic compounds
conduct electricity?