Element 85 in our International Year of the Periodic Table series is astatine. Astatine is incredibly scarce on Earth, and there’s so little of it around that we don’t know a great deal about it.

Astatine’s name literally means unstable – it’s derived from the Greek ‘astatos’. It lives up to its name admirably, with its most stable isotope having a half-life of just over 8 hours.

Astatine is one of the rarest naturally abundant elements on Earth. It’s estimated that the top kilometre of the entire Earth’s crust contains no more than 50 milligrams of astatine at any given time.

Due to this scarcity and instability, we don’t know a great deal about many of astatine’s properties. We don’t know what it looks like, because even if we could assemble a sample of it big enough to see, it would be vaporised by its own radioactivity. It’s thought that, based on the trends down the halogen group, it’s likely to be a black solid.

Unsurprisingly, astatine doesn’t have any applications of note!

Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page.