About half a year ago I’ve read and reviewed an interesting little book called Periodic Table: A Very Short Introduction. Like most other such books in the “Very Short Introduction” series it managed to reintroduce a seemingly familiar concept in a new and updated form. It also held a few surprises. In my mind the properties of the periodic table were well understood in terms of the non-relativistic quantum mechanics, and in fact were the most straightforward application of that branch of theoretical physics. It turns out, which was news to me, that many of the properties of the heavier elements need the use of relativistic quantum mechanics for their full explanation.

I’ve gotten to know Eric Scerri, the author of that book, pretty well. He is very interested in the subtleties of the periodic table and atomic physics in general, and has recently started a new blog where he talks about soem other interesting properties of the atomic structure of elements that are either not well known, or are downright misrepresented in the standard textbook treatments. Lately he’s been addressing the so called Aufbau principle – the principle that supposedly gives a unique way of filling up the electron orbits of atoms. The principle is based on the atomic structure of Hydrogen, the simplest atom and the only one that we are able to understand exactly. It seems that extrapolating from that simple atom to the others in the periodic table is not always straightforward, and in fact the aforementioned principle has many exceptions. I won’t go into all the details, and you are more than welcome to check Eric’s blog for further information. As a Physicist, this interests me because it implies that quantum mechanics may still hold many secrets, especially when it comes to nontrivial many-body problems. This looks like an interesting theoretical problem, and something well worth pursuing as a research project.