1 Response Sheet Questions  Why do we need to know the shapes of big molecules? What exactly would it tell you? How is this related to the side effects of drugs?  How do we make different molecules? What are some important molecules?

2 Response Sheet Questions  Will there eventually be synthetic everything once we figure out the molecular structure of everything?  What is an organic compound?

3 Response Sheet Questions  Why is chemistry (molecular science) a “supremely visual science” if we can’t see atoms?  Why are x-rays so hard to focus?  Why aren’t metals made of molecules?

4 Types of Solid Materials  Arrangements of Atoms in Solids  Amorphous – no long range order  examples include many plastics, rubber, and glass  Crystalline – regular repeating pattern  Types of Solids  molecular solids - discrete molecules (I 2 )  metallic solids - metal atoms, metallic bonding (Fe)  network covalent solids - strong interatomic bonding (examples include diamond and graphite)  ionic solids - individual ions are held together by electrostatic forces

5 The Unit Cell  Definition: the unit cell is a collection of atoms (or fractions of atoms) that can be systematically translated through space to create the entire solid  In two dimensions, unit cells take the shape of parallelograms  In three dimensions, they are parallelepipeds

6 Stoichiometry  take NaCl, for example  8 Cl on corners / 8 cells = 1  6 Cl on faces / 2 cells = 3  12 Na on edges / 4 cells = 3  1 Na in center / 1 cell = 1  Overall: Na 4 Cl 4 or NaCl  now look at TiO 2 (rutile)  1 Ti in center / 1 cell = 1  8 Ti on corners / 8 cells = 1  4 O on faces / 2 cells = 2  2 O within cell / 1 cell = 2  Overall: Ti 2 O 4 or TiO 2

7 Cubic Unit Cells simple cubic body-centered cubic (bcc) face-centered cubic (fcc)

8 Modern Materials  Liquid Crystals  Polymers (addition/condensation, x-link)  Metals (memory metal)  Ceramics (superconductors)  Thin films (MOCVD)  Semiconductors

9 Materials Chemistry  Basic types of materials  metals  polymers / plastics  ceramics  Applications  electronics, automobiles, clothing fibers, containers, coatings, biomaterials, sports equipment, superconductors, etc.

10 “Memory Metal” martensitedeformed martensite austenite deform heat cool

11 Memory Metal Applications

12 Polymeric Materials  Polymers are long-chain molecules formed by the polymerization of small “monomers”  Types of polymerization  Addition (polyethylene, polypropylene, Teflon, etc.)  Condensation (Nylon, polyesters, Kevlar, etc.)

13 Kevlar fiber poly(p-phenylene terephthalamide)

14 Electrically Conducting Polymers  Addition polymerization of acetylene (C 2 H 2 ) yields polyacetylene  When polyacetylene is oxidized or reduced (doped), it becomes electrically conductive!

15 Photolithography  Begin with Doped Silicon Substrate  Grow Oxide Layer  Apply Photoresist Polymer  Place Mask over Chip  Expose Areas to be Removed to Light  Remove Mask  Wash Away Exposed Photoresist  Etch Oxide Layer  Deposit Next Layer  Remove Remaining Photoresist silicon wafer

16 Light-Emitting Diodes (LED’s)  LED’s emit light when electrons fall from the conduction band into the valence band  LED’s are solid solutions of gallium, phosphorous and arsenic: GaP (1–x) As x  Different compositions produce different colors

17 Solid Solutions

18 High T Superconductors  It was discovered in 1911 that mercury loses all resistance to electrical flow when cooled to approximately 4 K  In 1986 Bednorz and Müller at IBM Zurich discovered superconductivity in copper- containing oxides at temperatures above 30 K!