How many different nuclei are out there? If you just take the number of distinct elements, you get 114, as of last month. But then there are the isotopes—elements which have an extra neutron (or two, or three, or more). The number of isotopes discovered so far is somewhere in the neighbourhood of 3,000.
How many isotopes there are in all depends on how large an atom can get before it can’t take on any more neutrons, and that, as it turns out is a surprisingly difficult thing to calculate. A new paper in Nature this week takes a stab at the limit and finds that there are probably in the neighbourhood of 7,000 isotopes in total that can exist (most of them briefly).
In related isotope news, Michael Thoennessen, a physicist at the National Superconducting Cyclotron Laboratory at Michigan State University in East Lansing, has released a new list of the top 25 isotope hunters in history (see below, click to make it bigger). Just as in his provisional list, released last year, two Germans and a Brit are at the top.
Given the space left in the nuclear landscape, there’s plenty of room for new scientists to edge their way into the top 25, but it may not be too likely to happen. Most of the 3,000 remaining isotopes are fleeting and very difficult to detect, and it seems likely that few of them will ever be seen.
That doesn’t mean that they don’t matter though. According to the authors of the Nature paper, the isotopes could still play brief but important roles in stellar processes and should be considered in theoretical calculations.
Credit: Stoitsov, M. et al.; M. Thoennessen, Discovery of Isotopes Project