Chapter 2 is titled "The Schrödinger Equation" and provides a short review of the basic principles of quantum mechanics, especially the Schrödinger equation and it's implications for the theory and things that are interesting to chemistry. The second page of the treatment of the Schrödinger equation looks as follows:
Note what is written in the red box:
The potential energy V is a result of electrostatic attraction between the electron and the nucleus. Attractive forces, like those between a positive nucleus and a negative electron, are defined by convention to have a negative potential energy. An electron near the nucleus (small r) is strongly attracted to the nucleus and has a large negative potential energy. Electrons farther from the nucleus have potential energies that are small and negative. For an electron at infinite distance from the nucleus (r = ∞), the attraction between the nucleus and the electron is zero, and the potential energy is zero.
The notation here is rather confusing, in my opinion. First, potential energy is attributed to an attractive interaction between the electron and the nucleus. OK, I can get behind that. In the next sentence, however, "attractive forces [...] have a negative potential energy." How can a force
Yes, this is not a physics textbook, but I'm sure we could find these kinds of inconsistencies in physics quantum textbooks, too. How are students supposed to understand energy, when even textbooks use inconsistent descriptions and notations?
If this textbook can be taken as an indicator, it might only mean that chemists don't need to think of forces/energy the same way physicists do. Joe Redish and collaborators in chemistry and biology have observed that different disciplines have different needs and priorities regarding energy. Their project, "Creating a Common Thermodynamics," is trying to negotiate a common approach to thermo stuff. Joe told me over lunch at AAPT that the different disciplines make very different assumptions and use the same general concept to mean three different things. It seems like stuff we might need to know about, since many of the teachers in our classes have a bio or chem background.
ReplyDeletehere's their project description:
ReplyDeletehttp://umdberg.pbworks.com/w/page/44279419/Creating%20a%20Common%20Thermodynamics
Even if it is true that chemists think differently about forces and energy (and I'm not sold on this yet, especially in this context), I still think that it is very confusing to attribute energy as a possession to three different things within the same paragraph, without elaborating/specifying further.
ReplyDelete