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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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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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Types of Bonding Ionic Covalent Metallic Van der Waals (Secondary)

The Periodic Table Columns: Similar Valence Structure give up 1e- 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 Columns: Similar Valence Structure Electronegative elements: Readily acquire electrons to become - ions. Electropositive elements: Readily give up electrons to become + ions. Adapted from Fig. 2.6, Callister & Rethwisch 8e. 7

Rule #2: Stable Configurations Some electron configurations are especially stable. (Think “noble gases”)

f06_02_pg23 Example: Na, Cl f06_02_pg23.jpg

Rule #1: Electrical Neutrality Opposites attract

1) Ionic Bonding Atoms take/give electrons to neighbor Often 1 metallic & 1 non-metallic (Elements from opposite sides of table)

2) Covalent bonding Atoms Share Electrons

f06_02_pg23 Example: H2O f06_02_pg23.jpg

2) Covalent bonding Adjacent atoms share electrons to achieve stable e- configuration

Reality check ionic covalent Nature of the bond reported as: Percent ionic character

3) Metallic Bonding Share electrons (“sea of electrons”) Orbitals never completely filled: Electrons jump from atom to atom

Secondary or Van der Waals Bonding Section 2.7 Secondary or Van der Waals Bonding

Rule #3: Dipoles almost always occur

4) Secondary (Van der Waals) bonding Weak compared to primary bonds Can significantly affect material properties

4) Secondary (Van der Waals) bonding Fluctuating induced dipole moments Before: Ion core Ion core – Ion core + After: – Ion core + –

4) Secondary (Van der Waals) bonding Permanent Dipole Bonds Permanent dipole moments in the molecule. Bonds stronger than for Fluctuating Example: H2O H H H – O + – O + – O + H H H

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)

Structure of Crystalline Solids Sections 3.1–3.4; 3.7 Structure of Crystalline Solids

Cubic xl Structures

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.

Crystal Systems Table 3.2

Crystal Systems, cont’d Table 3.2, cont’d

Unit cell f04_03_pg46 Cubic System a = b = c a = b = g = 90º Fig. 3.4 f04_03_pg46.jpg Fig. 3.4

Atomic Packing Factor APF = volume of atoms in unit cell total volume of unit cell

Metallic xl Structures Face-Centered Cubic (FCC) Body-Centered Cubic (BCC) Hexagonal Close-Packed (HCP)

FCC f02_03_pg42 Atoms at 8 corners & 6 faces Equivalent of ? whole atoms. Atomic Packing Factor (APF)= .74 f02_03_pg42 f02_03_pg42.jpg Fig. 3.1

FCC Cubic structure STM of Platinum Dept. Kings.edu/chemlab, Property of IBM

What’s an STM image? http://en.wikipedia.org/wiki/Scanning_tunneling_microscope A scanning tunneling microscope (STM) is an instrument for imaging surfaces at the atomic level.

You are under our control! Atoms…. You are under our control!

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.

FCC examples Lab-grown copper (SEM) Etched Aluminum (SEM) 0.3 mm Lab-grown copper (SEM) Etched Aluminum (SEM) Galena (Pb ore) Gold

What’s an SEM image? http://en.wikipedia.org/wiki/Scanning_electron_microscope A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with electrons in the sample, producing various signals that can be detected and that contain information about the sample's surface topography and composition. A scanning electron microscope (SEM) produces images by scanning a sample with a focused beam of electrons. Yields topography and composition.

BCC f02_03_pg42 Atoms at 8 corners & 1 in center of cube f02_03_pg42.jpg Atoms at 8 corners & 1 in center of cube Equivalent of ? whole atoms APF = .68 Fig. 3.2

BCC Cubic structure STM of Aluminum (100) surface https://wiki.fysik.dtu.dk/dacapo/Examples

BCC examples Molybdenum Iron

Metallic xl Structures Face-Centered Cubic (FCC) Cu, Al, Ag, Au, Pb, Ni, Pt Body-Centered Cubic (BCC) Na, Fe, Cr, Mo, W Hexagonal Close-Packed (HCP) Ti, Zn, Cd, Co, Mg

f07_03_pg54 Hexagonal System a1 = a2 = a3 ≠ z = 90º g = 120º Fig. 3.7 f07_03_pg54.jpg Fig. 3.7

HCP f03_03_pg43 Atoms at 12 corners, 3 in interior, 2 centered on basal planes Equivalent of ? whole atoms (APF)= .74 f03_03_pg43.jpg Fig. 3.3

Hexagonal structure STM of Nickel surface structure. Dept. Kings.edu/chemlab, Property of IBM

Hexagonal structure Zinc hand sample 45

Hexagonal structure SEM of Fine Cadmium powder SEM of ZnO nanowires http://www.lac.tu-clausthal.de/en/arbeitsgruppen/angewandte-photonik-lac/projekte/zinc-oxide-nanowires-for-photonic-applications/ http://www.sciencephoto.com/media/8998/enlarge

HCP Examples Cadmium crystal bar Titanium crystals Magnesium (SEM)

Atomic Packing Factors BCC = 0.68 FCC = 0.74 HCP = 0.74