Francium (Fr)

Francium is a chemical element with symbol Fr and atomic number 87. It was discovered by Marguerite Perey in France in 1939. It is the second-most electropositive element, behind only cesium, and is the second rarest naturally occurring element.

Atomic Number

87

Atomic Mass

223 u

Category

alkali metal

Phase

solid

Density

1.87 g/cm³

Electron Shells

2, 8, 18, 32, 18, 8, 1

Atomic Structure

Protons: 87 • Electrons: 87 • Neutrons: Varies by isotope

Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s¹

Discovery

1939 • Marguerite Perey