Oh quantum mechanics... It has been quite fun and challenging to try to introduce you to a young group of general chemistry students this past week. I enjoyed the opportunity to tell the story of how experimental evidence didn't match the classical physics theory. I always like talking about the discoveries found when we are carefully observant - when we look for something beautiful - something that strikes us with awe. Within that small crack of deviation between the theory and observation, there existed a whole realm beyond what any had even imagined. It is still difficult for us to imagine or even begin to describe... and here I am, I'm trying to "teach" about particle-wave duality, intelligently, in a way that a student could begin to grasp at this crazy concept proposed by Prince de Broglie... I must admit I don't even try to do this without a wink and a smile, readily admitting that this is difficult for us to wrap our minds around...
Today when I was describing a node in an electron orbital as a region of zero electron density, one of my students asked "but how does the electron get to the other side of the node?" I smiled mischeviously (maybe even laughed lightly) and said "good question," then paused, and asked if anyone else had any questions... The class laughed together and the student himself responded saying, "well I guess it has to do with the wavelike property of the electron particle and how it is delocalized over the entire orbital." LOVE IT when they answer their own question - well answer it with at least as good of an answer as I could give them to this mind boggling question...
Wednesday, I was discussing whether an orbital "exists" if it is not occupied by an electron. I was explaining the way I think about it is that it exists whether or not there is electron density in it (whether or not there is an electron). For most thinking on atomic and molecular orbitals, my way of thinking works out for me. BUT I readily admit that if someone wants to argue the opposite way (that if the definition of an orbital is a region of electron density... then the orbital is only a possibility and not a reality if there is not any electron in it), THEN I'd readily let them win the argument... because in reality this is along the same lines of - "which came first - the chicken or the egg?" And in the end, we'd both be describing the same reality and actually both have an understanding of the underlying concept being discussed. I said "what we are really doing here is attempting to describe a reality with words and our words are limited and all our analogies break down at some point." It has been refreshing to know that I'm in good company on this point. Some of my favorite science quotes come from the fathers of quantum mechanics
"When it comes to atoms, language can be used only as in poetry. The poet, too, is not nearly so concerned with describing facts as with creating images." - Niels Bohr
"Quantum theory provides us with a striking illustration of the fact that we can fully understand a connection though we can only speak of it in images and parables." -Heisenberg
As a teacher, I'm sometimes surprised by the random images, analogies, and stories that end up coming out of my mouth as I try to demonstrate a point. For instance: With regards to precipitation reactions, I talk about people hooking up at a party. With regards to the photoelectric effect, I actually talked about a photon putting up bail to get an electron out of jail. Oh yeah - and I talked about Harry Potter in class - I was trying to make the point that the students have a quantized address just like an electron (theirs is dorm, floor, room, & bed, like the electron's is shell, subshell, orbital, & spin) In this quantized world, you could live on floor one or floor two, but not floor 1.3... Then I said, "but the platform in Harry Potter violates this quantization principle". I asked them what was its number again and they responded in pretty near unison "it is platform 9 and 3 quarters"
So, this is my recounting of some highlights from teaching on this (it still surprises me how fun i think teaching this is). I've also had some thought connected to these concepts. Specifically thinking about the delocalization of sin. Also, thinking about how our lives, our transitions, are not like the transitions of the electrons from one level to another with no halfway or partway in between possible. perhaps i'll write more about these thoughts in the days to come...
