Difference between illinium and promethium
- a soft silvery metallic element of the rare earth group having no stable isotope; was discovered in radioactive form as a fission product of uranium
Mythological characters that can be found on the periodic table include Tantalus (Tantalum, Ta) and his daughter Niobe (Niobium, Nb), and Promethius (Promethium, Pm).
In fact, the elements with atomic numbers 43, 61, and 85 (technetium, promethium, and astatine, respectively) were unknown on earth until some of their radioactive isotopes had been produced synthetically.
The only missing one was element number 61, which was eventually isolated from the debris of the radioactive decay of uranium and given the name of promethium, after the Greek god who gave man fire.