Astatine

Astatine is the rarest naturally occurring element to exist on Earth. It’s a radioactive element listed on the Periodic Table with the atomic number 85 and the symbol At. The elements name comes from the Greek word Astatos which means unstable. Astatine is a semi-metal that results from the decay of uranium and thorium. Its half-life is barely 8 hours which means it becomes something else in less than 24 hours. Namely bismuth or polonium isotopes. Really...