Francium

Atomic symbol: Fr
Atomic number: 87
Atomic mass: 223

Appearance: Solid at 25°C

Group: 1
Period: 7
Series: Alkali metals
Block: s
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶ 7s¹

2nd rarest naturally occurring element and 2nd most electropositive element.

Highly reactive, and very radioactive with a short half-life.

Fun Fact! Of the first 100 elements of the Periodic Table, francium is the most unstable.