Which Chemical Element Is the Hardest to Find?

Astatine is the most rare naturally-occurring element on Earth. In fact, scientists know very little about this radioactive semi-metal, which forms during the decay of uranium and thorium. Physicists have to infer many of the element’s properties -- such as its radioactive properties, its conduction qualities, and its color -- and it’s thought that only about 25 grams occur naturally on the planet at any given time. In addition to its scarcity, astatine doesn’t last very long. Astatine-210, the element’s most stable form, has a half-life of 8.1 hours, which means that it you found some, half of it would be gone after a typical workday.

It might be, it could be:

• The element has an atomic number (85), an atomic symbol (At) and an atomic weight (210). The element's name is derived from the Greek word astatos, which means unstable.
• Astatine is the heaviest known element in the halogen group. Halogens have low melting and boiling points, are brittle when solid, and are poor conductors of heat and electricity.
• Some scientists think astatine might be a good cancer fighter, though its scarcity makes research difficult. It's way more scarce than diamond, a pure element from carbon or gold. It might behave like iodine, they say, which tends to collect in the thyroid. Once there, its radioactivity could zap cancerous cells.