Interstudio 2 September 15, 2004

Interstudio 2 Outline Warm up Recap aspects of studio in first week Atomic models How do we see atoms today? Atomic orbitals & electron configurations (PT S2) Office Hour today 4:30-5:30 Textbook?

Concept Question 1 Which of the following samples could be methane, CH4?  A sample that contains: (a) 25% hydrogen by weight; 75% carbon by weight (b) 4.0 g of H atoms and 1.0 g of C atoms (c) 0.40 mole of H atoms and 1.0 x 1023 C atoms (d) 0.40 mole of H2 molecules and 0.20 moles of C atoms  

Concept Question 2 Antoine Lavoisier, the "father of chemistry", listed lime as a chemical element in his table of 33 known elements. Which of the following observations best shows that lime cannot be an element? Lime reacts with water, generating a large amount of heat. Lime and carbon dioxide are produced when limestone is roasted. When a certain soft metal is burned in oxygen, lime is produced (with no other products). Lime melts at a temperature of 2572°C.

Concept Question 3 What is the approximate number of carbon atoms it would take placed next to each other to make a line that would cross this dot: • 4 200 30,000,000 6.02 x 1023

Groups Evaluation after first exam Skirky (2003) in his provocatively titled "A group is its own worst enemy", highlights three types of self-defeating patterns identified by Bion in groups: pairing off (e.g. flirtation) the identification and vilification of external enemies (e.g. 'Microsoft' or 'management') religious veneration (things that may not be criticized)

Homework Models of atom extra OWL Number/type of problem will vary Strategy Working with one another (know that you will be responsible individually on exam) Random guess

SEA FAQs: Does the unknown have to go in one special place? Presentation reminders (ask questions) Evaluation

Lab Report Formatting Purpose Experimental Results Citations Figures, Graphs, Tables Purpose Experimental Results Citations Grading Rubric How long should each section be? What should they include? In your own words.

Zhao,Y. ; Chen, Z. ; Yuan,H. ; Gao, X. ; Qu, L. ; Chai, Z. ; Xing, G Zhao,Y.; Chen, Z.; Yuan,H.; Gao, X.; Qu, L.; Chai, Z.; Xing, G.; Yoshimoto, S.; Tsutsumi, F.; Itaya, K. “Highly Selective and Simple Synthesis of C2m-X-C2n Fullerene Dimers” J.Am. Chem. Soc. 2004, 126, 11134 – 11135.

Sworen, J.C.; Smith, J.A.; Berg, J.M.; Wagener, K.B. J. Am. Chem. Soc. 2004, 126, 11238-11246.

Fact, Law, Theory, Model What models/theories have you encountered? Why study models, especially those that have been updated/disproven? Why the ethics discussion? What about Rutherford’s experiment? All giving you situations that scientists encounter as you prepare to be a scientist. Lead into lab reports (results)

How many models has the Periodic Table survived? Thompson’s Cathode Ray tube 1897 (electricity that set them up 1891-1898) Milikan 1909-1913 Plum pudding (Thompson) Bohr (1913) Quantum (modern)

How many models has the Periodic Table survived? Thompson cathode ray tube (1891-1898) (other electric charge experiments) Plum pudding Milikan 1909-1913 Bohr 1913 Quantum Periodic table (1871) Thompson’s Cathode Ray tube 1897 (electricity that set them up 1891-1898) Milikan 1909-1913 Plum pudding (Thompson) Bohr (1913) Quantum (modern)

Models of Molecules H2O

Seeing Atoms and Molecules Naked eye Optical microscope Electron microscope

Electron Microscope 1930s Image ~12 atom molecule Must be used under vacuum Electrons waves and particles Focused using magnets Look at image on fluorescent screen Shorten wavelength; increase energy; destroy sample Images from: www.vetref.net/ emscope/theorysch.html

SEM Images Images from: www2.ijs.si/~goran/ semmate2.html Pollen from daisy, pollen from violet, paper Images from: www2.ijs.si/~goran/ semmate2.html

STM (Scanning Tunneling Microscope) 1983 STM 1986 Nobel Laureates Heinrich Rohrer and Gerd Binnig http://nobelprize.org/physics/educational/microscopes/scanning/

STM (Scanning Tunneling Microscope) A tip is scanned over a surface at a distance of a few atomic diameters in a point-by-point and line-by-line fashion. At each point the tunneling current between the tip and the surface is measured. The tunneling current decreases exponentially with increasing distance and thus, through the use of a feedback loop, the vertical position of the tip can be adjusted to a constant distance from the surface.

STM 2. The amount of these adjustments is recorded and defines a grid of values which can be displayed as a grayscale image. 3. Instead of assigning the values to a color we can also use them to deform the grid in the direction perpendicular to the surface. 4. Now we can bring back the grayscale and paint each square according to an average of the four defining grid points. Movement controlled by piezoelectric crystals –materials that change shape in a reproducible vay when a voltage is applied across them

STM images of elements and atoms Surface must be an electrical conductor nickel iron on copper copper The Kanji characters for "atom." The literal translation is something like "original child." http://www.almaden.ibm.com/vis/stm/atomo.html

Atomic Force Microscopy 1985 Technique can directly resolve nanoscale features: 0.2nm in Z, 1-2nm in X, Y. Can function in air and in fluids.

How It Works Laser beam is reflected off the back of the cantilever as it is raster scanned across the surface. When tip encounters a feature on the surface, displacement of the cantilever results in displacement of the laser beam on the detector. For example, if the tip scans across a feature projecting from the sample surface, the cantilever will deflect upwards and the resultant laser spot on the detector will be displaced lower.

Basic Mode 1: Contact Mode In contact mode, the tip is constantly in touch with the sample surface. Similar to a record player, the sample is moved underneath the tip. The tip reads the “bumps and grooves” in the sample surface, only instead of converting these bumps and grooves into music, the AFM converts them into a topographic image. http://www.inkyfingers.com/RECORD/CECILEX/Cecil7.html

Basic Mode 2: Tapping Mode Tapping mode, or intermittent contact mode, is often used for softer samples such as polymers or biological samples. Tip is oscillated by a piezoelectric crystal. As the tip approaches and interacts with the sample, the amplitude of the oscillation is decreased. A feedback loop measures the reduction in amplitude, which translates into a topographic image.

Surface Characterization TappingModeTM AFM image of disc surface CD-R 10µm x 10 µm Image obtained from Digital Instruments website: http://www.di.com/NanoTheatre/theater.html

Using AFM to Studio Programmed Cell Death (Apoptosis) -16 min. 16 min. 48 min. 1 hr 20 min. 1 hr 52 min. 2 hrs 24 min. Distance (µm) Height (µm)

More AFM Images Zhao,Y.; Chen, Z.; Yuan,H.; Gao, X.; Qu, L.; Chai, Z.; Xing, G.; Yoshimoto, S.; Tsutsumi, F.; Itaya, K. “Highly Selective and Simple Synthesis of C2m-X-C2n Fullerene Dimers” J.Am. Chem. Soc. 2004, 126, 11134 – 11135.

Need models to conceptualize what we cannot see What is an orbital?

Atomic Orbitals and Electron Configurations Periodic Trends Studio 2 (p22) p orbitals d orbitals f orbitals