Copernicium

For a strangely huge number of reasons, it's difficult not to think of copernicium as one of the strangest substances in the entire planet. Copernicium was originally synthesized in 1996 and has only ever existed in a lab, to name a few. Its half-life is around 29 seconds. It has only ever been present in exceedingly minute amounts. Although not verified, it is thought to be a metal. It is also assumed that, at room temperature, it would either be a gas or a volatile liquid. That much strangeness in one ingredient is a lot.

We're not exaggerating when we claim that it was only present in trace amounts. It was initially made by bombarding lead-208 with zinc-70 nuclei. Thus, copernicium was created in a single atom. We don't know whether it is a metal or a gas at room temperature in part because of this. It's difficult to determine from one atom. The atom disintegrated relatively instantly.