Ununennium

Ununennium was the 25th synthesized element on Earth, it was the only synthesized element which wasn't highly radioactive, but still had a short half-life of 2.3 million years.

History
Ununennium was synthesized by Particle Physicist in the Feldsman Super Collider. 2 Praseodymium atoms were collided together at speeds fast enough to force the two atoms nucleons to bond. A large radioactive burst occurred but was partially neutralized, making the atom not so radioactive. This was in 2025. Ununnenium had no particular use until 2213 when Politium was discovered, a naturally occurring non-synthetic 119 element.

Present Role
As of the 25th century, Ununnenium and it's fore comers have no significant usage except being historical atoms showing humanities ancient abilities of atomic synthesis.