Chem7.2.ppt

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7.2 Ionic Bonds and Ionic Compounds >

Chapter 7 Ionic and Metallic Bonding

7.1 Ions

7.2 Ionic Bonds and

Ionic Compounds

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7.2 Ionic Bonds and Ionic Compounds >

CHEMISTRY

&

YOU

Where does table salt come from?

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7.2 Ionic Bonds and Ionic Compounds >

Formation of Ionic

Compounds

Formation of Ionic Compounds

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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.

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7.2 Ionic Bonds and Ionic Compounds >

Formation of Ionic

Compounds

Although they are composed of ions,

ionic compounds are electrically

neutral.

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7.2 Ionic Bonds and Ionic Compounds >

Formation of Ionic

Compounds

Ionic Bonds

• The electrostatic forces that hold ions

together in ionic compounds are called

ionic bonds

.

Anions and cations have opposite charges

and attract one another by means of

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7.2 Ionic Bonds and Ionic Compounds >

Formation of Ionic

Compounds

Ionic Bonds

• Sodium and chlorine atoms combine in a

one-to-one ratio, and both ions have stable octets.

When sodium and chlorine react to form a

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7.2 Ionic Bonds and Ionic Compounds >

Formation of Ionic

Compounds

Ionic Bonds

• Each bromine atom has seven

valence electrons and readily

gains one additional electron.

• Three bromine atoms

Aluminum metal (Al) and

the nonmetal bromine (Br

₂

)

react violently to form the

ionic solid aluminum

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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.

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7.2 Ionic Bonds and Ionic Compounds >

Formation of Ionic

Compounds

Formula Units

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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

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7.2 Ionic Bonds and Ionic Compounds >

Formation of Ionic

Compounds

Formula Units

For sodium chloride, the lowest

whole-number 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

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7.2 Ionic Bonds and Ionic Compounds >

Use electron dot structures to

predict the formulas of the ionic

compounds formed from the

following elements:

Sample

Problem 7.1

Sample

Problem 7.1

Predicting Formulas of Ionic Compounds

a.

potassium and oxygen

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7.2 Ionic Bonds and Ionic Compounds >

Analyze

Identify the relevant concepts.

1 Sample

Problem 7.1

Sample

Problem 7.1

• Atoms of metals lose valence electrons

when forming an ionic compound.

• Atoms of nonmetals gain electrons.

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7.2 Ionic Bonds and Ionic Compounds >

a.

Start with the atoms.

Solve

Apply the concepts to this problem.

2 Sample

Problem 7.1

Sample

Problem 7.1

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7.2 Ionic Bonds and Ionic Compounds >

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.

Solve

Apply the concepts to this problem.

2 Sample

Problem 7.1

Sample

Problem 7.1

K

•

• O

••

•

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7.2 Ionic Bonds and Ionic Compounds >

a.

Express the electron dot structure as a

formula.

Solve

Apply the concepts to this problem.

2 Sample

Problem 7.1

Sample

Problem 7.1

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7.2 Ionic Bonds and Ionic Compounds >

b.

Start with the atoms.

Solve

Apply the concepts to this problem.

2 Sample

Problem 7.1

Sample

Problem 7.1

Mg and

N

•

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7.2 Ionic Bonds and Ionic Compounds >

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.

Solve

Apply the concepts to this problem.

2 Sample

Problem 7.1

Sample

Problem 7.1

•

• N

•

• Mg

•

• _•

• N

••

_•

• 3–

2+

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7.2 Ionic Bonds and Ionic Compounds >

b.

Express the electron dot structure as a

formula.

Solve

Apply the concepts to this problem.

2 Sample

Problem 7.1

Sample

Problem 7.1

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7.2 Ionic Bonds and Ionic Compounds >

Use electron dot structures to

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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.

• ••

_•

F

•

• +

Ca

2+

F

• ••

_•

•

• –

Ca

•

• _•

• _F

••

_•

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7.2 Ionic Bonds and Ionic Compounds >

Properties of Ionic

Compounds

Properties of Ionic Compounds

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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

three-dimensional patterns.

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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.

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7.2 Ionic Bonds and Ionic Compounds >

Properties of Ionic

Compounds

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7.2 Ionic Bonds and Ionic Compounds >

Would you expect to find sodium

chloride in underground rock deposits

as a solid, liquid, or gas? Explain.

CHEMISTRY

&

YOU

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7.2 Ionic Bonds and Ionic Compounds >

Would you expect to find sodium

chloride in underground rock deposits

as a solid, liquid, or gas? Explain.

CHEMISTRY

&

YOU

CHEMISTRY

&

YOU

Sodium chloride is found in

underground rock deposits

as a solid. Like most ionic

compounds, sodium

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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

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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

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7.2 Ionic Bonds and Ionic Compounds >

Properties of Ionic

Compounds

Titanium dioxide (TiO

₂

), or rutile,

forms tetragonal crystals.

• The coordination

number for the cation

(Ti

4+

) is 6.

• The coordination number

– Each Ti

4+

ion is surrounded

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7.2 Ionic Bonds and Ionic Compounds >

Properties of Ionic

Compounds

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7.2 Ionic Bonds and Ionic Compounds >

Properties of Ionic

Compounds

When sodium chloride is melted, the orderly

crystal structure breaks down.

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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,

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7.2 Ionic Bonds and Ionic Compounds >

Properties of Ionic

Compounds

Ionic compounds also conduct electric

current if they are dissolved in water.

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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

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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

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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.

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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

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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

MgCl

₂

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7.2 Ionic Bonds and Ionic Compounds >

• 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

BIG

IDEA

BIG

IDEA

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7.2 Ionic Bonds and Ionic Compounds >

END OF 7.2