Francium (Fr)


  • Symbol: Fr
  • Atomic Number: 87
  • Atomic Weight: [223]
  • Element Classification: Alkali Metal
  • Discovered By: Marguerite Perey
  • Discovery Date: 1939
  • Name Origin: Named after France, the country of its discovery
  • Density(g/cc): Estimated to be around 1.87 (predicted)
  • Melting Point: 27°C (estimated)
  • Boiling Point: 677°C (estimated)
  • Appearance: Presumed to be a highly radioactive metal; actual appearance is unknown due to its extreme rarity and radioactivity
  • Atomic Radius(pm): Estimated to be about 260


Francium was discovered in 1939 by Marguerite Perey at the Curie Institute in Paris, France. Perey identified francium as a decay product of actinium-227, filling the last remaining gap in the periodic table for naturally occurring elements at that time. It was named “francium” in honor of France, reflecting the nationality of its discoverer and the tradition of naming elements after countries or regions.

Relation to Other Elements

Francium is a member of the alkali metals, which also includes lithium, sodium, potassium, rubidium, and cesium. As the heaviest known alkali metal, francium exhibits characteristics typical of the group, such as a single electron in its outer shell, which it readily loses to form +1 ions. Francium is highly reactive and metallic, although its properties are largely extrapolated from its position in the periodic table due to its scarcity and intense radioactivity.

Natural Occurrence

Francium is one of the rarest and most radioactive naturally occurring elements. It is estimated that there are no more than a few grams of francium in the Earth’s crust at any given time. Francium occurs naturally in uranium and thorium ores as a result of the radioactive decay of actinium. Due to its short half-life, with the most stable isotope, francium-223, having a half-life of only 22 minutes, francium is not found in significant amounts and is studied only in minute quantities.


Due to its extreme rarity, short half-life, and radioactivity, francium has no significant commercial applications. Its use is primarily confined to scientific research, particularly in atomic and nuclear physics experiments to study the properties of alkali metals and to investigate the structure of atomic nuclei.

The discovery of francium provided important verification for the periodic table and contributed to the understanding of radioactive decay series. Although it has no practical uses, francium remains of interest to scientists for theoretical and experimental research in understanding the properties of heavy alkali metals and the behavior of radioactive elements.


Radon (Rn)

Radium (Ra)