Chem7.3.ppt

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7.3 Bonding in Metals >

Chapter 7 Ionic and Metallic Bonding

7.1 Ions

7.2 Ionic Bonds and

Ionic Compounds

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7.3 Bonding in Metals >

CHEMISTRY

&

YOU

What are some properties that are

unique to metals?

Wrought iron is a very

pure form of iron that

contains trace

amounts of carbon. It

is a tough, malleable,

ductile, and

corrosion-resistant material that

melts at very high

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic Properties

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic Properties

How can you model the valence

electrons of metal atoms?

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

The valence electrons of atoms in a

pure metal can be modeled as a sea

of electrons.

• The valence electrons are mobile and

can drift freely from one part of the

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Metallic bonds

are the forces of

attraction between the free-floating

valence electrons and the positively

charged metal ions.

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Properties of Metals

Metals are good conductors of electric

current because electrons can flow

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Properties of Metals

Metals are good conductors of electric

current because electrons can flow

freely in the metal.

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Metals are ductile—that is, they can be

drawn into wires.

Properties of Metals

Force

Metal

rod

Die

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Metals are ductile—that is, they can be

drawn into wires.

• Metals are also

malleable, which

means that they can

be hammered or

pressed into

shapes.

Properties of Metals

Force

Metal

rod

Die

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

When a metal is subjected to pressure, the

metal cations easily slide past one another.

Properties of Metals

Sea of

electrons

Metal

cation

Force

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

When a metal is subjected to pressure, the

metal cations easily slide past one another.

• If an ionic crystal is struck

with a hammer, the blow

tends to push the positive

ions close together.

• The positive ions repel

one another, and the

crystal shatters.

Properties of Metals

Sea of

electrons

Metal

cation

Force

Metal

cation

Strong

repulsions

Nonmetal

anion

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7.3 Bonding in Metals >

How are metals and ionic compounds

different? How are they similar?

CHEMISTRY

&

YOU

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7.3 Bonding in Metals >

How are metals and ionic compounds

different? How are they similar?

CHEMISTRY

&

YOU

CHEMISTRY

&

YOU

Both metals and ionic compounds form

crystal structures. However, they have

different configurations of electrons. The

sea of electrons surrounding cations in a

metal allows metals to be ductile and

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Crystalline Structure of Metals

For spheres of identical size, such as metal atoms,

several closely packed arrangements are possible.

• These Thai oranges illustrate

a pattern called a hexagonal

close-packed

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Crystalline Structure of Metals

In a body-centered cubic structure, every atom

(except those on the surface) has eight neighbors.

• The metallic

elements sodium,

potassium, iron,

chromium, and

tungsten crystallize

in a body-centered

cubic pattern.

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Crystalline Structure of Metals

In a face-centered cubic arrangement, every atom

has twelve neighbors.

• Among the metals

that form a

face-centered cubic

structure are copper,

silver, gold,

aluminum, and lead.

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7.3 Bonding in Metals >

Metallic Bonds and Metallic

_Properties

Metallic Bonds and Metallic

_Properties

Crystalline Structure of Metals

In a hexagonal close-packed arrangement, every

atom also has twelve neighbors.

• Metals that have a

hexagonal

close-packed crystal

structure include

magnesium, zinc, and

cadmium.

Zinc

_{• The pattern is different from the}

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7.3 Bonding in Metals >

Which of the following models can

describe the valence electrons of metals?

A. A body-centered cube

B. Octets of electrons

C. A rigid array of electrons

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7.3 Bonding in Metals >

Which of the following models can

describe the valence electrons of metals?

A. A body-centered cube

B. Octets of electrons

C. A rigid array of electrons

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7.3 Bonding in Metals >

Alloys

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7.3 Bonding in Metals >

Alloys

Why are alloys important?

• Alloys

are mixtures of two or more elements,

at least one of which is a metal.

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7.3 Bonding in Metals >

Alloys

Alloys are important because their

properties are often superior to

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7.3 Bonding in Metals >

Alloys

Alloys are important because their

properties are often superior to

those of their component elements.

• Sterling silver (92.5 percent

silver and 7.5 percent

copper) is harder and more

durable than pure silver, yet

it is still soft enough to be

made into jewelry and

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7.3 Bonding in Metals >

Alloys

The most important alloys today are steels.

• The principal elements in most steels, in addition to

iron and carbon, are boron, chromium, manganese,

molybdenum, nickel,

tungsten, and vanadium.

• Steels have a wide

range of useful

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7.3 Bonding in Metals >

Alloys

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7.3 Bonding in Metals >

Alloys

Alloys can form from their component atoms in different ways.

• If the atoms of the components in an alloy are

about the same size, they can replace each

other in the crystal.

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7.3 Bonding in Metals >

Alloys

Alloys can form from their component atoms in different ways.

• If the atoms of the components in an alloy are

about the same size, they can replace each

other in the crystal.

– This type of alloy is called a substitutional alloy.

• If the atomic sizes are quite different, the

smaller atoms can fit into the interstices

(spaces) between the larger atoms.

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7.3 Bonding in Metals >

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7.3 Bonding in Metals >

Explain why alloys are important, and

list one important alloy.

Alloys are important because they often have

properties that are superior to those of the

elements from which they are made. Stainless

steel is an important alloy because of its

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7.3 Bonding in Metals >

Key Concepts

The valence electrons of atoms in a

pure metal can be modeled as a sea of

electrons.

Alloys are important because their

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7.3 Bonding in Metals >

Glossary Terms

• metallic bond:

the force of attraction that

holds metals together; it consists of the

attraction of free-floating valence electrons for

positively charged metal ions

• alloy:

a mixture composed of two or more

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7.3 Bonding in Metals >

• Metals are made up of closely packed

cations surrounded by a sea of

electrons.

• The sea-of-electrons model explains

why metals are good conductors of

electric current and why they are ductile

and malleable.

BIG

IDEA

BIG

IDEA

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7.3 Bonding in Metals >