classicalkhlennium: A while ago I was talking with my friend about the presence of isotopes in Mistborn, and we thought surely the metals have ions and isotopes like they do in the real world, otherwise how else would they exist on an atomic level?
We wondered if there were radioactive isotopes on Scadrial or even in the Cosmere as a whole, else they would never discover nuclear weaponry and fuels. None of the non-god metals in Mistborn have radioactive components, but that isn't to say that radioactive metals don't exist in the cosmere. Radioactive elements such as uranium (a necessary discovery for the 3rd and 4th Eras of Mistborn if they want to have long term fuel sources/weapons) and radium (necessary discovery in the field of medicine) seem necessary to the advancement of civilization.
This also raises the question of where would the god metals, lerasium, atium, and harmonium, fit on the Periodic Table, and would all of their isotopes be stable, would they perhaps have radioactive isotopes that can somehow affect their Allomantic properties?
Brandon Sanderson: These are things we'll start answering in the modern day Mistborn novels, so RAFO for now.