Making Sense of Electrons, Atoms, and Molecules

The discovery of the electron in 1897 was followed just 14 years later by the discovery of the atomic nucleus in 1911. In 1913 Bohr proposed a model of the hydrogen atom in which the electron made perfectly circular orbits around the newly discovered nucleus (proton) only to see his theory replaced by Schrödinger’s more general theory, wave mechanics, in 1926. Wave mechanics has dominated the thinking of chemists ever since, but it has hardly been the last word on the matter. More subatomic particles have been discovered, and other forms of quantum mechanics have been suggested over the years (matrix mechanics, density functional theory, …) including theories (quantum electrodynamics, quantum chromodynamics, …) that go far beyond the simplistic thinking of chemists.

So what really happens when two electrons, or perhaps an electron and a positively charged nucleus, get really, really close to each other? Wave mechanics turns to Coulomb’s law for help, and Coulomb states that the force between these particles varies inversely with the square of the distance between them, that is, the force is proportional to 1/r^2. This would imply that the force (and the potential energy associated with it) approaches infinity as r approaches zero. This can lead to disturbing thoughts (what keeps electrons from ‘falling into’ the nucleus?) and disturbing mathematical problems (how do I work with a formula that busts its way to infinity?).

Nautilus recently emailed me an old article (“The Trouble with Theories of Everything”, 1 Oct 2015) that looks into these disturbing corners of science and concludes, “There is no known physics theory that is true at every scale—there may never be.” Coulomb’s law, wave mechanics, you name it – are designed to explained certain phenomena that appear on certain scales of time, space, energy, and so. It may be possible to extrapolate them to other scales successfully, but there are no guarantees. Caveat extrapolator!

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Elemental Haiku

Carbon, C

Show-stealing diva,

throw yourself at anyone,

decked out in diamonds.

And that pretty much sums it up. Carbon is awesome.

Interested in seeing how the other elements fare when filtered through haiku paper? Check out Elemental Haiku (Science, 4 Aug 2017) or, even easier, find them in this interactive periodic table.

Note: element 119 has not been synthesized yet so the poet has already gone where no scientist has been (yet).

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Protecting Your Eyes During Next Week’s Eclipse and Beyond

What’s so special about the sunlight during an eclipse? Isn’t it the same old sunlight we see the rest of the time?

Yes, it is, but because the event is so interesting to look at, and because the normally blinding solar disk is partly blocked out, the temptation is to look, and look, and look. See “Chemistry explains why you shouldn’t stare at the solar eclipse without proper protection” (C&ENews, print 21 Aug 2017, online 14 Aug 2017).

The article explains the photochemical events that trigger retinal damage (the “heat” of the sunlight is not to blame) and it describes several options for safe viewing of the Sun. Here’s a bit from the article: Continue reading

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READ ME – this blog is dormant through Fall, 2018

This web page will not be maintained during the 2017-18 academic year. All course-related materials should be obtained from the appropriate Moodle pages. This site will resume business in Fall, 2018.

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Retrieval Practice Protects Your Memory

A new article in Science magazine from Prof. Ayanna Thomas’ research group is one that every O Chem student should look at. The article doesn’t contain any chemistry, but it contains some potentially valuable insights into becoming a more successful O Chem student.

Continue reading

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Drop-In Tutors for Finals

The DoJo will have drop-in tutoring available 7-9 PM for Chem 201 on Sat (12/10) and Mon (12/12).

Sam and Alan will also be in their offices for drop-in-consultation for much of Th/F/M/Tu/W, weather permitting.

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O chem slowing you down? Try FOH!

Some of you may be suffering from FMOOWMP. You know the symptoms, but you probably didn’t know that help was close at hand. And it’s painless. Here’s a short video to bring you up-to-speed. https://youtu.be/yQq1-_ujXrM

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Distractions Are Everywhere

I heard a presentation from a neuroscientist last week on how our brains work. She highlighted different brain networks that one can imagine working well in some situations (“keep an eye out for tigers and snakes”), but get corrupted into un-, even counter-productive activities in modern circumstances (“keep an eye out for tweets”). We all have these networks and we all live in a world filled with more, and more round-the-clock, stimuli than our ancestors could have ever imagined. Staying on task gets more challenging all the time. Here’s an article from the NY Times Education section that might offer some helpful insights and tips: How to Deal with Digital Distractions (Times, 1 Nov 2016).

You can also test your ability to resist distractions right now: try not clicking on this post from 2013, Like Ketchup on Sushi, that takes you to another Times article, How to Get an A- in Organic Chemistry.

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The Right Kind of Practice

What single thing must you do to learn organic chemistry? Sam and I have given you the answer several times: practice solving problems. But is that all you have to do? Can you just open the book to a problem, work on it, and learn organic chemistry? Maybe you can, maybe you can’t. Not all practice makes perfect.

Continue reading

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SN2 Reaction Animation

Predicting the outcome of an “opposite side attack” SN2 reaction can be confusing at first, but animations can help. Check out the SN2 animation at chemtube3D.com. To operate the animation, find the drawing of the chemical reaction and click on the forward reaction arrow.

Try to understand the simple reaction from multiple perspectives: 1) the C seems to push its way through its 3 H neighbors to get from leaving group to nucleophile, OR 2) the 3 H neighbors seem to back away from the approaching nucleophile and move to the leaving group’s side of the molecule. You can rotate the animation as it plays so that you can see it from different angles.

Another SN2 animation to watch: HS(-) + (S)-PhCHClCH3

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