The Qualitative Analysis Lab is now posted. Log into the student area and go to the laboratory resources.

Today we began the study of atomic orbitals and periodic properties. I hope you all can explain why the chlorine atom is smaller than the sodium atom but the sodium cation is much smaller than the chloride anion. We looked at the shapes of the orbitals the: s, p, d, f orbitals (so please don’t freak out).

You should be able to draw the s, p and d orbitals. We discussed the Aufbau principle of filling atomic orbitals. You should be able to write electronic configurations (1s² etc.) for any element up to Xenon. One way to visualize the atomic orbitals is to use the Orbitron. Be sure to click on the different tabs: wave function, electron density, etc.

We haven’t talked about Schrödinger’s Cat so I hope you will watch this video. This is a very famous gedanken (thought experiment) that underscored the odd behavior that occurs at the quantum level of matter. This little experiment has made it’s way into popular culture so it is useful to have some idea what it is all about.

Next week we will discuss bonding, shapes of molecules, and molecular orbitals. Exam Two is on Thursday July 15th. Please be aware that Exam Three comes just one week later on July 22nd.

Today we carefully went over the last two quizzes. The gas law quiz will be repeated tomorrow after class for anyone who hopes to earn a better score. The key point is that it is important to classify a problem type to know how to proceed. The main three types of gas law problems are ones based on the combined gas law (changes in conditions), ones based on the ideal gas law (usually combined with stoichiometry), and ones about density (learn the density equation).

The thermodynamics quiz was a bit better but many errors were made from a kind of carelessness. It is very important to order your thoughts and to order your work – take up the space you need.

After working on the quizzes for awhile we took a sparkler break. The chemistry of fireworks typically involves a strong oxidizing agent like potassium chlorate or potassium nitrate. Both of these provide oxygen that is then used to support the combustion of other materials.

After our break it was back to quantum chemsitry. You should know the three main experiments that could not be explained by classical physics, the ten scientists and their major contribution to atomic theory, and the rules for the four quantum numbers: n, l, m_l, and s. Each quantum number tells us something about the electrons in orbitals: size, shape, orientation and electron spin. The contours we see for these orbitals are deceptive – the orbitals are probability equations. They predict the probablity of finding an electron in a certain place. The electrons have specific energies, quantized energies. They move from one orbital to another by the absorption and emission of photons. (We also looked at the vocabular of light interactions with matter.)

All in all it was a very busy day.

Thanks to Meridith for this beautiful photograph taken during laboratory. This shows the chameleon-like behavior of iodine – one color in a polar solvent (dark orange) and a different color in a non-polar (hexane) solvent – deep violet. These different colors arise as a result to ligand field interactions with d-orbitals of iodine. Ligand field interactions are discussed in Chemsitry 203.

Iodine was first discovered in 1811 and named for its beautiful violet color (iodes means violet in Greek). Iodine is frequently used as an antiseptic agent. Tincture of iodine is a solution of iodine in ethanol.

“One day in 1811, Courtois made a mistake. He added too much sulfuric acid to the mixture. He was amazed to see clouds of beautiful violet vapor rising from the mixture. He decided to study the new material. Eventually, he proved it was a new element. He named the element after its color. In Greek, the word iodes means ‘violet.’”

Read more about iodine at Chemsitry Explained.