Download - If you are not registered for ChE 361
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If you are not registered for ChE 361
Please come see me
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About Clicker Quizzes:
1) Review previous lectures
2) Review reading assignment
3) Assess understanding of today’s discussion
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The Clicker Trials•Register your i>clicker by Monday, 27 January(Registration info posted on Canvas, click on link).
•You can take part in polling before registering, but scores will not be posted to Canvas until you register.
•If your i>clicker is already registered for another course, there is no need to register again.
•If you make a mistake registering, just re-register. i<clicker will accept the most recent registration.
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Clicker Quizzes• You may consult with your neighbors, unless directed otherwise.
• You may consult with your text, but time is limited.
• Correct answer = 2 points Incorrect answer=1 point
• I drop the lowest 2 clicker grades to allow for absences/clicker problems/forgotten remotes.
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1. Power on your clicker
i>clicker will power off after 90 minutes of inactivity.
i>clicker2 will power off after 5 minutes of inactivity.
2. When the polling begins, Press the letter corresponding to your answer.i>clicker–green light=answer accepted; flashing red=try again.
i>clicker2–a check mark ( √ )will show up beside your answer on LCD screen.
3. Ask if you need help
The Clicker Games-let’s try this!
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Types of Bonding
• Ionic
• Covalent
• Metallic
• Van der Waals (Secondary)
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The Periodic TableColumns: Similar Valence Structure
Adapted from Fig. 2.6, Callister & Rethwisch 8e.
Electropositive elements:Readily give up electronsto become + ions.
Electronegative elements:Readily acquire electronsto become - ions.
giv
e u
p 1
e-
giv
e u
p 2
e-
giv
e u
p 3
e-
ine
rt g
ase
s
acc
ept
1e
-
acc
ept
2e
-
O
Se
Te
Po At
I
Br
He
Ne
Ar
Kr
Xe
Rn
F
ClS
Li Be
H
Na Mg
BaCs
RaFr
CaK Sc
SrRb Y
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Some electron configurations are especially stable.(Think “noble gases”)
Rule #2: Stable Configurations
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Example: Na, Cl
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Opposites attract
Rule #1: Electrical Neutrality
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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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Example: H2O
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2) Covalent bondingAdjacent atoms share
electrons to achieve stable e- configuration
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Reality check
ionic covalent
Nature of the bond reported as:Percent ionic character
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3) Metallic Bonding• Share electrons (“sea of
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
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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
+Ioncore
–
–
Fluctuating induced dipole moments
–
Ion core
Before:
After:
Ion core
Ion core +
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• Permanent Dipole BondsPermanent dipole moments in the molecule.Bonds stronger than for Fluctuating
• Example: H2O
OHH +– O
HH +– O
HH +–
4) Secondary (Van der Waals) bonding
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For which will VdW forces have the strongest influence on properties?Covalent bond: Where a rod meets a ball
A.Graphite(Carbon)
B.Diamond(Carbon)
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Sections 3.1–3.4; 3.7
Structure of Crystalline
Solids
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Cubic xl Structures
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Unit Cell
• Smallest structural unit that generates a 3-D xl (if repeated).
• 7 Crystal Systems—Only 7 unit cell shapes for all xl structures.
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Table 3.2Crystal Systems
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Table 3.2, cont’d
Crystal Systems, cont’d
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Unit cell
Cubic Systema = b = c
º
Fig. 3.4
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Atomic Packing Factor
APF = volume of atoms in unit cell
total volume of unit cell
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Metallic xl Structures
1) Face-Centered Cubic (FCC)
2) Body-Centered Cubic (BCC)
3) Hexagonal Close-Packed (HCP)
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FCCAtoms at 8 corners & 6 faces
Equivalent of ? whole atoms.
Atomic Packing Factor (APF)= .74
Fig. 3.1
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FCC Cubic structure
STM of PlatinumDept. Kings.edu/chemlab, Property of IBM
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A scanning tunneling microscope (STM) is an instrument for imaging surfaces at the atomic level.
What’s an STM image?
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Atoms….
You are under our control!
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• 1990: IBM scientist Don Eigler used an STM to move single xenon atoms on a nickel surface
•The engineers moved 35 atoms to spell out "IBM" in a 10 micrometer logo.
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FCC examples
Lab-grown copper (SEM)0.3 mm
Etched Aluminum (SEM)
GoldGalena (Pb ore)
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A scanning electron microscope (SEM) produces images by scanning a sample with a focused beam of electrons. Yields topography and composition.
What’s an SEM image?
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BCC
Atoms at 8 corners & 1 in center of
cube
Equivalent of ? whole atoms
APF = .68Fig. 3.2
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BCC Cubic structure
STM of Aluminum (100) surface
https://wiki.fysik.dtu.dk/dacapo/Examples
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BCC examples
Molybdenum Iron
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Metallic xl Structures
1) Face-Centered Cubic (FCC)Cu, Al, Ag, Au, Pb, Ni, Pt
2) Body-Centered Cubic (BCC)Na, Fe, Cr, Mo, W
3) Hexagonal Close-Packed (HCP)Ti, Zn, Cd, Co, Mg
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HexagonalSystem
a1 = a2 = a3 ≠ z
º
º
Fig. 3.7
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HCP
Atoms at 12 corners, 3 in interior, 2 centered on basal planes
Equivalent of ? whole atoms
(APF)= .74Fig. 3.3
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Hexagonal structure
STM of Nickel surface structure.
Dept. Kings.edu/chemlab, Property of IBM
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Zinc hand sample
Hexagonal structure
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SEM of Fine Cadmium powder
http://www.sciencephoto.com/media/8998/enlarge
SEM of ZnO nanowireshttp://www.lac.tu-clausthal.de/en/arbeitsgruppen/angewandte-photonik-
lac/projekte/zinc-oxide-nanowires-for-photonic-applications/
Hexagonal structure
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HCP Examples
Titanium crystals
Cadmium crystal bar
Magnesium (SEM)
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Atomic Packing Factors
BCC = 0.68 FCC = 0.74 HCP = 0.74