© Copyright Pearson Prentice Hall Slide 1 of 25 Ionic Bonds and Ionic Compounds In many coastal countries that have warm, relatively dry climates, salt

© Copyright Pearson Prentice Hall

Slide 1 of 25

Ionic Bonds and Ionic Compounds

In many coastal countries that have warm, relatively dry climates, salt is produced by the evaporation of seawater. You will learn how cations and anions combine to form stable compounds such as sodium chloride.

7.2

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> Formation of Ionic Compounds

Compounds composed of cations and anions are called ionic compounds.

Although they are composed of ions, ionic compounds are electrically neutral.

The charges of the ions balance each other and the compound has no charge

7.2

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Aluminum metal and the nonmetal bromine react to form an ionic solid, aluminum bromide.

7.2

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Ionic Bonds

The electrostatic forces that hold ions together in ionic compounds are called ionic bonds.

7.2

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Formula Units

• A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance.

• A formula unit is the lowest whole-number ratio of ions in an ionic compound.

7.2


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NaCl is the chemical formula for sodium chloride.

7.2


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Conceptual Problem 7.2


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Properties of Ionic Compounds

Properties of Ionic Compounds

What are three properties of ionic compounds?

–Most ionic compounds are crystalline solids at room temperature.

–Ionic compounds generally have high melting points

–Ionic compounds are brittle

7.2

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> Properties of Ionic Compounds

The orderly arrangement of component ions produces the beauty of crystalline solids.

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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.

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In CsCl, each ion has a coordination number of 8.

In TiO2, each Ti4+ ion has a coordination number of 6, while each O2- ion has a coordination number of 3.

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Ionic compounds can conduct an electric current when melted or dissolved in water.

7.2

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> Bonding in Metals

You have probably seen decorative fences, railings, or weathervanes made of a metal called wrought iron. In this section, you will learn how metallic properties derive from the way that metal ions form bonds with one another.

7.3

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> Metallic Bonds and Metallic Properties

The valence electrons of metal atoms can be modeled as a sea of electrons.

The valence electrons are mobile and can drift freely from one part of the metal to another.

Metallic bonds consist of the attraction of the free-floating valence electrons for the positively charged metal ions.

7.3

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Metals are ductile—that is, they can be drawn into wires.

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A force can change the shape of a metal. A force can shatter an ionic crystal.

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> Crystalline Structure of Metals

Crystalline Structure of Metals

These tomatoes have a closed-packed arrangement. Similar arrangements can be found in the crystalline structure of metals.

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> Crystalline Structure of Metals

Metal atoms are arranged in very compact and orderly patterns.

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> Alloys

Alloys are mixtures composed of two or more elements, at least one of which is a metal.

Alloys are important because their properties are often superior to those of their component elements.

7.3

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> Alloys

Bicycle frames are often made of titanium alloys that contain aluminum and vanadium.

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> Alloys

The most important alloys today are steels. Steels have a wide range of useful properties, such as corrosion resistance, ductility, hardness, and toughness.

7.3


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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

7.2 Section Quiz.

7.2 and 7.3.


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1. Which chemical formula is incorrect?

a. KF2

b. CaS

c. MgO

d. NaBr

7.2 Section Quiz.


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2. Ionic compounds can 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.

7.2 Section Quiz.


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3. At room temperature, most ionic compounds are

a. crystalline solids.

b. liquids.

c. gases.

d. soft, low melting-point solids.

7.2 Section Quiz.


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1. The valence electrons of metals can be modeled as

a. a body-centered cube.

b. octets of electrons.

c. a rigid array of electrons.

d. a sea of electrons.

7.3 Section Quiz.


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2. In most metals, the atoms are

a. free to move from one part of the metal to another.

b. arranged in a compact and orderly pattern.

c. placed at irregular locations.

d. randomly distributed.

7.3 Section Quiz.


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3. Alloys are important because they

a. are pure substances.

b. are the ores from which metals can be refined.

c. can have properties superior to those of their components.

d. are produced by the combustion of metals.

7.3 Section Quiz.

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© Copyright Pearson Prentice Hall Slide 1 of 25 Ionic Bonds and Ionic Compounds In many coastal countries that have warm, relatively dry climates, salt