While researching the radioactive decay of actinium-227, francium was discovered by Marguerite Perey in 1939 at the Curie Institute in Paris. The element’s name comes from its country of discoveryFranceand was the last naturally occurring element discovered by scientists. All other elements have subsequently been created in the lab. On the periodic table, Francium-223 (Fr ) formerly known as actinium-K, has the atomic element number 87 and is made naturally when actinium-227 emits an alpha-particle preceding— element 88 (radium). Francium-223 and francium-221 are the only isotopes that occur naturally, although francium-223 is far more common. Synthetically, francium can be created by means of the following formula: 197Au + 18O → 210Fr + 5 n.
Characteristics of Francium
Due to francium’s radioactivity and rarity its melting point is uncertain. It is the least electronegative heavy metal with only 22 minutes of half-life and is very unstable. The natural occurrence of francium on the Earth is 20-30 g ( 1 oz.) and is the second rarest element found in its crust next to astatine. Thus, the estimated boiling point value of francium is 677 .° Because francium is found in such small quantities, it is unknown how it would react with water. Scientists theorize that due to its volatile nature, it would react more violently than sodium or cesium. There are no uses for francium commercially due to its instability and rarity and has been most recently studied at Stony Brook University, New York for research purposes. At the university, scientists were able to harness up to 10,000 francium atoms simultaneously by using laser beams in a magnetic field to measure the atom’s properties.
Abundance and Isotopes
Francium has mass numbers ranging in atomic mass from 199 to 232 with 34 known isotopes. Francium-223 has the longest half-life and is the most stable. It has one valence electron as an alkali metal. With a half life of only 0.12 μs, the ground state isotope francium-215, is the least stable. In a natural setting francium is found in thorium minerals and uranium ores in small amounts. As the isotopes in francium breakdown, they either turn into radium, astatine or radon. The largest amount of synthetic isotopes produced in the laboratory was a cluster of more than 300,000 atoms.
In the lab setting, francium can be combined with perchloric acid or silicotungstic acid without another alakli metal carrier and can also bind with several caesium salts, silicotungstate, iodate, rubidium tartrate, chloroplationate, picrate, and caesium perchlorate. This provides other methods of separation, since nearly all francium salts are water soluble. Francium has been used in the fields of atomic structure and biology research. Francium was once considered as a possible aid for various cancers diagnoses, but this type of application has since been viewed as futile to pursue.
Francium’s basic atomic structure and its ability to be created synthetically, harnessed, and cooled has made it an ideal element to be used in specialized spectrascopy tests. These tests have led to more specific information regarding the subatomic particles and energy levels. Light given off by francium-210 laser-trapped ions have provided scientists accurate data between atomic energy levels changes that somewhat resemble those foreseen by quantum theory.
