Francium is the chemical element with the chemical symbol Fr, and atomic number 87. The name of the element comes from English France, the country of its discovery. It is thought that it melts easily compared to its kin of Caesium and Rubidium, and may have a density of ~2.48 g/cm3. Its appearance and practical chemistry can be confidently predicted.
The only isotope of Fr occurring naturally in significant amounts is 223Fr, a descendant of 235U. 223Fr decays by beta emission, releasing 1.15 MeV worth of energy in the process. A bit of playing with numbers reveals that a 1 mm diameter sphere of 223Fr puts out an average of 245 watts during its first half-life, most of which remains inside the specimen. Within about 0.005 sec, the sphere will turn into a tiny nuclear fireball at a temperature approaching 2000 K. While no macroscopic sample can be obtained without high-order magic, a sample of some 200000 atoms (5E-16 micromole) emitted enough light to allow it to be photographed (see picture).
Often hailed as the most reactive Alkali Metal, it is thought perhaps it may be less reactive than Caesium, as Francium's lone 7s electron spends a part of its time close to the nucleus. In order to do that, the electron must have so much kinetic energy that it becomes more massive - causing its orbital to shrink. A 7s electron spends very little time near the nucleus, so its increasing bond strength and decreasing orbital radius are noticiable but not dramatic.
Discovered in 1939 by French chemist Margeurite Perey, Francium was discovered in a pure sample of Actinium, which had higher energy than thought. This energy hence was coming from another element - this would be Francium. The heaviest of the known Alkali Metals, Francium is produced only in atomic quantities for research. Like other Alkali Metals, it has a single valence electron.
- Melting Point: 21°C, 70°F, 294 K
- Boiling Point: 650°C, 1202°F, 923 K
- Electron Configuration: [Rn] 7s1
Because of its instability, Francium has no applications. It is impractical for use in radiotherapy, because its half-life is to short as for it to be readily transported.