Exam review
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361_02_bonding_c.pptWe will use
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The two primary factors that affect the structure of a material are
- Performance and properties
- Composition and performance
- Composition and processing
- Processing and performance
PRACTICE CLICKER QUESTION #1
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Performance
Processing
Structure
Composition
Properties
Interrelationships
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Primary Classes of Materials
Examples of changes in composition
- Metals—increase C content of Fe
- Ceramics—Substitute K with Ca
- Polymers—Substitute H with F
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Performance
Processing
Structure
Composition
Properties
Interrelationships
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Processing
Clay becomes Fired clay pottery
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SEM: Clay vs. Fired Clay
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2
3
Discrete clay & quartz particles melt & fuse into vitreous material.
Processing affects structure
Processing: Copper
Copper Tubing
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Processing
Metal Ore Mine
Processing: Copper
Copper Ore
Smelting Process
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Processing: Copper
99.9% Pure copper
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Performance
Processing
Structure
Composition
Properties
Interrelationships
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Structures—all scales
Example: BCC crystal: Molybdenum
Subatomic
Atomic
Microscopic
Macroscopic
Performance
Processing
Structure
Composition
Properties
Interrelationships
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Properties
Brittleness
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Properties
Response to imposed stimulus.
[If I drop it (stimulus), will it break (response)?]
- mechanical
- electrical
- thermal
- deteriorative
- magnetic
- optical
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Mechanical Property:
Elasticity–recoverable deformation
Paper clip
under normal use
Mechanical Property:
Plasticity—permanent deformation
Paper clip
under abuse
Plasticity by design
Radial profile
segments
Plasticity by accident
Street lamp
damaged during
storm
(Bridgeport, CN)
Mechanical Property:
Brittleness
Pressure vessel fails during hydraulic test
Deteriorative Property:
Corrosiveness
Corroded ship at Guantanamo
Properties of copper ore vs refined copper
Response to imposed stimulus.
- Mechanical
- Electrical
- Thermal
- Deteriorative
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The Humble Hanger
The Humble Hanger
Coat hanger in 1880s schoolhouse
Performance
Processing
Structure
Composition
Properties
Humble Hanger:
What determines performance?
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PRACTICE CLICKER QUESTION #2
Which of the following are considered material properties?
- Metals, ceramics, polymers
- Strength, conductivity, brittleness
- Increasing the Si/O2 ratio
- Cubic, orthorhombic, tetragonal
PRACTICE CLICKER QUESTION #3
Which of the following are examples of changes in composition?
- Increasing strength
- Increasing size of a crystal
- Increasing the Si/O2 ratio
- Changing the crystal structure
- Applying more heat
PRACTICE CLICKER QUESTION #3
Which of the following are examples of changes in processing?
- Increasing strength
- Increasing size of a crystal
- Increasing the Si/O2 ratio
- Changing the crystal structure
- Applying more heat
Chapter 2
Periodic Table:
2.1, 2.2, 2.4
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Practice Clicker Question #3—Reading Assignment
The number of electrons in an electrically neutral atom is described by:
- The atomic mass
- The atomic number
- The mole
- The isotope ratio
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From W. D. Callister (2007) Materials Science and Engineering: An Introduction, 7/e. New York: Wiley & Sons
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Periodic Table of the Elements
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f06_02_pg23.jpg
Practice Clicker Question #4—Reading Assignment
If you were asked to identify elements from the periodic table that have similar chemical and physical properties, which would you choose?
- Elements that lie in the same row
- Elements that lie in the same column
- Elements that lie along a diagonal
- None of the above: Properties vary
dramatically between neighboring elements
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f06_02_pg23
Alkali Metals
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f06_02_pg23.jpg
f06_02_pg23
Alkali Earth
Metals
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f06_02_pg23.jpg
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Transition Metals
Non-metals
Intermediate
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Transition—partially filled d states, and in some cases, one or two electrons in the next higher energy shell.
Intermediate—characteristics are intermediate between metals and non-metals because of their valence electron structures. Semi-conductors, metallic luster, tend to be brittle.
Non-metals—insulators, tend to be brittle, gain or share electrons
f06_02_pg23.jpg
Transition Metals
Workhorse of the periodic table: structural integrity, conductors
Intermediates
Semi-conductors, metallic luster, too brittle for structural integrity
Nonmetals
Insulators, brittle,
readily gain/share electrons
Transition—partially filled d states, and in some cases, one or two electrons in the next higher energy shell.
Intermediate—characteristics are intermediate between metals and non-metals because of their valence electron structures. Semi-conductors, metallic luster, tend to be brittle.
Non-metals—insulators, tend to be brittle, gain or share electrons
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Chapter 2
Bonding:
2.6–2.8
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Bohr Atomic Model
Sodium
Rules of bonding
1. Ordinarily, matter is electrically neutral.
2. Some electron numbers are especially stable
3. Dipoles almost always occur.
(Important to secondary bonding)
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Rule #1: Electrical Neutrality
Some electron configurations
are especially stable.
(Think “noble gases”)
Rule #2: Stable Configurations
f06_02_pg23
Noble Gasses
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f06_02_pg23.jpg
The Periodic Table
• Columns: Similar Valence Structure
Adapted from Fig. 2.6, Callister & Rethwisch 8e.
Electropositive elements:
Readily give up electrons
to become + ions.
Electronegative elements:
Readily acquire electrons
to become - ions.
give up 1e-
give up 2e-
give up 3e-
inert gases
accept 1e-
accept 2e-
O
Se
Te
Po
At
I
Br
He
Ne
Ar
Kr
Xe
Rn
F
Cl
S
Li
Be
H
Na
Mg
Ba
Cs
Ra
Fr
Ca
K
Sc
Sr
Rb
Y
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f07_02_pg24
Electronegativites
Fig. 2.7
Tend to increase:
left to right and bottom to top
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Electronegativity—tending to accept electrons
f07_02_pg24.jpg
Covered later in lecture
Rule #3: Dipoles
Section 2.6
Primary Interatomic Bonds
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Types of Bonding
- All but Noble gases are unstable
Type of bonding depends on
how to gain stability
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Types of Bonding
- Ionic
- Covalent
- Metallic
- Van der Waals (Secondary)
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Practice Clicker Question #5—Reading Assignment
Ionic bonding involves
- Sharing of electrons
- Electrostatic forces
- Dipole bonds
- Valence electrons moving among atoms to form a “sea” of electrons
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Some electron configurations
are especially stable.
(Think “noble gases”)
Rule #2: Stable Configurations
f06_02_pg23
Example: Na, Cl
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f06_02_pg23.jpg
Opposites attract
Rule #1: Electrical Neutrality
1) Ionic Bonding
Atoms take/give electrons to neighbor
- Often 1 metallic & 1 non-metallic
(Elements from opposite sides of table)
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2) Covalent bonding
Atoms Share Electrons
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f06_02_pg23
Example: H2O
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f06_02_pg23.jpg
2) Covalent bonding
Adjacent atoms share electrons to achieve stable e- configuration
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Reality check
ionic
covalent
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3) Metallic Bonding
- Share electrons
- Orbitals never completely filled:
Electrons jump from atom to atom
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Section 2.7
Secondary or Van der Waals Bonding
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Rule #3: Dipoles
almost always
occur
4) Secondary (Van der Waals) bonding
- Weak compared to primary bonds
- Can significantly affect material properties
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4) Secondary (Van der Waals) bonding
+
Ion
core
–
–
Fluctuating induced dipole moments
–
Ion
core
Before:
After:
Ion
core
Ion
core
+
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4) Secondary (Van der Waals) bonding
- Permanent Dipole Bonds
Permanent dipole moments in the molecule.
Bonds stronger than for Fluctuating
- Example: H2O
O
H
H
+
–
O
H
H
+
–
O
H
H
+
–
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Permanent dipole moments
+
+
–
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f07_02_pg24
Electronegativites
Fig. 2.7
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f07_02_pg24.jpg
Practice Clicker Question #6
Materials which are ionically bonded tend to have these two mechanical properties:
- Hard and brittle
- Hard and ductile
- Soft and brittle
- Soft and ductile
- None of these
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