TPT needs more radioactive elements IMO. So here are a two ideas:

TRIT - Tritium gas, occasionally emit high-speed electrons and glows

U235 - Uranium 235, fissile version of Uranium with radioactive decay, occasionally emit protons and neutrons.

Fakenublet:

...Uses? You're supposed to give us some "uses" for element suggestions, the devs don't want to add elements in the game that are just sitting on the screen just to look pretty.

They would be sources of subatomic particles similar to ISOZ. The two elements provide a source of electron, proton, and neutron. I see it as a way of allowing the creation of new nuclear reactors, etc.