Atomic number: 85
Density at 25°C: solid: density: uncertain
This is perhaps one of the rarest and fleeting elements that can naturally occur. It was initially synthesised but then later discovered in nature.
Use, natural applications or common combinations:
- naturally, albeit briefly, occurs in uranium minerals, estimated to only be about 1 gram on earth at anyone time.
- Francium-223, the father isotope of astatine-219, alpha decays with a probability of only 0.006%, making this astatine isotope extremely rare.