Astatine

Atomic symbol: At
Atomic number: 85
Atomic mass: (210)

Appearance: Unknown, solid at 25°C

Group: 17
Period: 6
Series: Metalloids
Block: p
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁵

Highly radioactive and very rare.

Due to its radioactive properties, it is used in medicine as a tracer and in some cancer treatments.

Fun Fact! Astatine is very rare; only about 25g of astatine naturally occurs in the world. That’s the weight of only 5x US nickel coins!