Chemistry 204 Dr. Don DeCoste 3014 Chemistry Annex decoste@illinois.edu 12-1 pm MWF (after lecture) 10-11 am Tuesdays and Thursdays By appointment; open door policy

Web Site https://chemistry.illinois.edu/clc Chemistry Learning Center site (CLC opens Tuesday, January 22). Will later include practice exams. Take time to explore (and make sure you can access OWL).

Similar, but Not the Same Discussion sections, OWL, exams Grading: 45% hour exams (15% each) 40% final exam 10% OWL 5% Discussion No Lon-Capa assignments. Access: Post questions to me (and class) Chemistry 202 videos (review if needed)

Chemistry 205: Lab Lab lectures begin Tu/Th this week. Go to lab this week for safety training. First lab next week!

Three Big Themes Content: specific topics in chemistry. Models: a way of explaining the phenomena we observe; theories. Understand significance and limitations. Problem Solving: be able to solve novel problems in a creative and flexible way using conceptual understanding of fundamental ideas; Challenge Problems in the text are good for this.

Richard Feynman All things are made of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed together.

Richard Feynman Quantum mechanics is the description of the behavior of matter and light in all its details and, in particular, of the happenings on an atomic scale.

Chemistry 202: No QM! Particulate nature of matter (stoich, gas laws, thermo, equil, kinetics) Chemical bonds Ionic through covalent Lewis structures VSEPR and polarity Properties such as boiling point

Various Atomic Models Dalton: Indivisible atoms J.J. Thomson: Atoms emit tiny negative particles. (Therefore atoms not indivisible!) Rutherford: Some α-particles bounce back when shot at atoms. (There is a concentration of mass with a positive charge in the atom.) http://www.youtube.com/watch?v=5pZj0u_XMbc

What Can’t We Explain? Lewis structures Why is O2 magnetic? Resonance structures? Odd number of electrons? Why is O2 magnetic? Why does O2+ have a stronger bond than O2? Why do some transition metal ions exhibit colors?

Big Ideas – Models Models are not reality. We use different models for different reasons. A model should be as simple as possible, but not simpler (Einstein) To answer more questions, the model must be more complex.

Quantum Mechanical Model Neils Bohr Anyone who is not shocked by quantum theory has not understood it. Richard Feynman I think I can safely say that no one understands quantum mechanics. Self-consistent Know the rules, no matter how strange (know ≠ understand).

Play By The Rules! When you land on a Licorice on the block by an exact count, you have to stay on the block and skip one turn. If you land on the Gooey Gumdrops, your pawn has to stay on the block until you draw a card with one or two yellow blocks. When you get lost in the Lollipop Woods, your pawn has to stay on the block until you draw a card with one or two blue blocks. When you are stuck in the Chocolate Swamp, your pawn has to stay on the block until you draw a card with one or two red blocks. The first person to land on the multicolored rainbow space and reach the Rainbow Castle has won the game.

Energy as “Light”

Energy Released

Everything is Quantized Matter is quantized: Atoms: 92 naturally occurring atoms. Molecules: can’t have “any” amount of water, for example. Energy is quantized: Photons Product of length and momentum or energy and time (units of Js, for example) is the same for all EMR. “Atom of action”: Planck’s constant 6.626 X 10-34 Js

Hydrogen Line Spectrum

A Change Between Two Discrete Energy Levels Emits a Photon of Light

A Change Between Two Discrete Energy Levels Emits a Photon of Light

Using Bohr’s Model

Particles or waves? Double slit experiment (“cannot explain…just tell”). Eddington: There was a time when we wanted to be told what an electron is. The question was never answered. No familiar conceptions can be woven around the electron; it belongs to the waiting list. [1928] A Tale of Two Nobels JJ Thomson: “proving” the electron is a particle. [1906] George Thomson (JJ’s son): “proving” the electron is a wave. [1937]