Because you can see how, after H and He, you do 2 loops of 8 and add the transition metals to the next 2 loops; then you add the lanthanides and actinides to the next 2 loops. And can easily see how the superactinides guy in the extended period table
What about the table of nuclides? IMO that’s the best way to list elements in a logically consistent manner. The trouble is, nature is a messy kraken that just won’t fit neatly into a shoe box. You can try to squeeze it in, but the lid won’t close because there are always a few tentacles sticking out.
For anyone who is wondering the alloy metal that is radioactive is Technetium #43. It is weird it has no stable isotopes, and is only one of two radioactive elements that proceed non radioactive elements. As far as I am concerned it exists only to be different.
Promethium #61 it is so rare that it really has no practical uses outside the lab. There is most likely less than a kilogram of the stuff in the entire planet.
