1. Section 4 Metallic Bonding
Chapter 6
Objectives
Describe the electron-sea model of metallic bonding, and explain why metals are good electrical conductors.
Explain why metal surfaces are shiny.
Explain why metals are malleable and ductile but ionic-crystalline compound are not.
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2. Bonding in Metals
6.4
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.
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3. The Metallic-Bond Model
Section 4 Metallic Bonding
Chapter 6
The Metallic-Bond Model
In a metal, the vacant orbitals in the atoms’ outer energy levels overlap.
This overlapping of orbitals allows the outer electrons of the atoms to roam freely throughout the entire metal.
The electrons are delocalized, which means that they do not belong to any one atom but move freely about the metal’s network of empty atomic orbitals.
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4. Metallic Bonds and Metallic Properties
6.4
Bonding in Metals
>
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.
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5. The Metallic-Bond Model
Section 4 Metallic Bonding
Chapter 6
The Metallic-Bond Model
These mobile electrons form a sea of electrons around the metal atoms, which are packed together in a crystal lattice.
The chemical bonding that results from the attraction
between metal atoms and the surrounding sea of
electrons is called metallic bonding.
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6. Chapter 6 Metallic Bonding
Visual Concepts
Chapter 6
Metallic Bonding
Click below to watch the Visual Concept.
Visual Concept
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7. Crystalline Structure of Metals
6.4
Bonding in Metals
>
Crystalline Structure of Metals
Crystalline Structure of Metals
How are metal atoms arranged?
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8. Crystalline Structure of Metals
6.4
Bonding in Metals
>
Crystalline Structure of Metals
These tomatoes have a closed-packed arrangement. Similar arrangements can be found in the crystalline structure of metals.
These tomatoes illustrate a pattern called a hexagonal close-packed arrangement.
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9. Crystalline Structure of Metals
6.4
Bonding in Metals
>
Crystalline Structure of Metals
Metal atoms are arranged in very compact and orderly patterns.
Metal atoms crystallize in characteristic patterns. a) Chromium atoms have a body-centered cubic arrangement. b) Gold atoms have a face-centered cubic arrangement. c) Zinc atoms have a hexagonal close-packed arrangement. Inferring Which of these arrangements is the most closely packed?
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10. Chapter 6 Metallic Bonding
Section 4 Metallic Bonding
Chapter 6
Metallic Bonding
Chemical bonding is different in metals than it is in ionic, molecular, or covalent-network compounds.
The unique characteristics of metallic bonding gives metals their characteristic properties, listed below.
electrical conductivity
thermal conductivity
malleability
ductility
shiny appearance
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11. Metallic Bonding, continued
Section 4 Metallic Bonding
Chapter 6
Metallic Bonding, continued
Malleability is the ability of a substance to be hammered or beaten into thin sheets.
Ductility is the ability of a substance to be drawn, pulled, or extruded through a small opening to produce a wire.
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12. Properties of Metals: Electrical and Thermal Conductivity
Visual Concepts
Chapter 6
Properties of Metals: Electrical and Thermal Conductivity
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Visual Concept
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13. Properties of Metals: Malleability and Ductility
Visual Concepts
Chapter 6
Properties of Metals: Malleability and Ductility
Click below to watch the Visual Concept.
Visual Concept
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14. Properties of Metals: Surface Appearance
Visual Concepts
Chapter 6
Properties of Metals: Surface Appearance
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Visual Concept
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15. Properties of Substances with Metallic, Ionic, and Covalent Bonds
Section 4 Metallic Bonding
Chapter 6
Properties of Substances with Metallic, Ionic, and Covalent Bonds
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16. Metallic Properties
* Metallic bond strength varies with the nuclear charge and the number of electrons in the metal’s electron sea.
*The enthalpy of vaporization is the amount of energy absorbed as heat when a specified amount of a substance vaporizes at constant pressure. This is a measure of the strength of the metallic bonds.
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17. Alloys Why are alloys important? 6.4 > Bonding in Metals Alloys 17
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18. 6.4
Bonding in Metals
>
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.
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19. 6.4
Bonding in Metals
>
Alloys
Bicycle frames are often made of titanium alloys that contain aluminum and vanadium.
Bicycle frames are often made of titanium alloys that contain aluminum and vanadium.
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20. 6.4
Bonding in Metals
>
Alloys
The most important alloys today are steels. Steels have a wide range of useful properties, such as corrosion resistance, ductility, hardness, and toughness.
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21. Assess students’ understanding of the concepts in Section 6.4.
6.4 Section Quiz.
Assess students’ understanding of the concepts in Section
6.4.
Continue to: Launch:
-or-
Section Quiz
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22. 1. The valence electrons of metals can be modeled as
6.4 Section Quiz.
1. The valence electrons of metals can be modeled as
a body-centered cube.
octets of electrons.
a rigid array of electrons.
a sea of electrons.
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23. 2. In most metals, the atoms are
6.4 Section Quiz.
2. In most metals, the atoms are
free to move from one part of the metal to another.
arranged in a compact and orderly pattern.
placed at irregular locations.
randomly distributed.
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24. 3. Alloys are important because they are pure substances.
6.4 Section Quiz.
3. Alloys are important because they
are pure substances.
are the ores from which metals can be refined.
can have properties superior to those of their components.
are produced by the combustion of metals.
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25. Online Self-Check Quiz
Complete the online Quiz and record answers. Ask if you have any questions about your answers.
click here for online Quiz 6.4
(7 questions)
You must be in the “Play mode” for the slideshow for hyperlink to work.
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26. Bonding in Metals
>
Concept Map 7
Concept Map 7 Solve the Concept Map with the help of an interactive guided tutorial.
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27. VIDEOS FOR ADDITIONAL INSTRUCTION
Additional Videos for Section 6.4: Metallic Bonding
Metallic Bond (2:30)
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