Fr

Francium

Identification

CAS Number: 7440-73-5

Discovery Year: 1939

Discoverer: Marguerite Derey

Discovery Location: France

Properties

Atomic Mass: 223 →Density: 1.87 g/cm³ →

Crystal Structure: BCC

Atomic Dimensions

Atomic Radius (Rahm): 258 pm

Covalent Radius: 260 pm →

Van der Waals Radius: 348 pm

Thermodynamics

Melting Point: 300 K →Boiling Point: 950 K →Heat of Fusion: 15 kJ/mol →

Electronic Structure

Electron Config: [Rn] 7s

Block: s

Period: 7 →Group: 1 →Electronegativity: 0.7 →Electron Affinity: 0.486 eV →

Oxidation States: +2

Abundance & Geochemistry

Geochemical Class: U/Th decay series

Goldschmidt Class: synthetic

About

Radioactive element, belongs to group 1 of the periodic table. Found in uranium and thorium ores. The 22 known isotopes are all radioactive, with the most stable being Fr-223. Its existence was confirmed in 1939 by Marguerite Perey.

Isotopes

Fr-212 212 ☢ 20.0 min

Fr-222 222 ☢ 14.2 min

Fr-223 223 ☢ 22.0 min