Table of Radioactive Isotopes (TORI_2) Issues
The primary key for the TORI_2 database is an ugly kluge called IZA, which may stand for “Isotope designator based on Z and A numbers”. That itself requires further explanation. Physicists, and possibly chemists, use Z to designate an element by its atomic number. (IFFY does the same, but calls it Protons, not Z.) Physicists use A for atomic weight. IZA multiplies the Z by 10,000 and adds the A, creating an integer that identifies each isotope uniquely. Isomers modify this by adding 300 for each energy level. There are 277 atomic weights, so these will be unique as well. Some isomers are four energy levels above the ground state, which means +1200. This is why Z is multiplied by 10,000. Multiplying by only 1000 might lead to duplicate IZA identifiers.
It is very common to use integers for the primary key. A key must be unique, and integers do that. It is also easy to add keys by adding one to the last key that was created. Database engines have an auto-number function to do that. When a new customer comes along, the database will associate her name with a new ID in the Customer table. Her records (purchases, payments, deliveries, etc.) will be spread across several tables. For ease of maintenance, you want to use her ID rather than her name in all these different places. If she gets married and her name changes, it only needs to be changed in the Customer table.
Since they can change, names are not often used as a primary key. But the names of isotopes/elements are very unlikely to change. (Exception: Super-heavy elements have place-holder Latin names until they are confirmed to exist. These are way beyond the range needed for IFFY.) So, we decided on a simpler and far more readable key – the name of the nuclide.
Just for grins, though, we have morphed IZA to EZA. In this scheme, the Energy (level) of the isomer is multiplied by a million. The proton number, multiplied by 1000, is added to that and then atomic weight. When sorted, the isomers will be lumped at the top or bottom of the list.