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Atomic Number: 87
Atomic Symbol: Fr
Atomic Weight: 223
Melting Point: 80.6 F (27 C)
Boiling Point: 1,251 F (677 C)
Word Origin: Francium was named for France, the country of its discovery.
Discovery: Marguerite Perey discovered francium in 1939 at the Curie Institute in Paris.
Properties of francium
Francium is both the heaviest of the known alkali metals and the most unstable of the first 101 elements in the Periodic Table. Additionally, it has the highest equivalent weight of any element. Francium’s chemical properties most resemble cesium. [See Periodic Table of the Elements]
There are 33 recognized isotopes of francium. 223Fr (Ac, K), a daughter of 227Ac, is the longest lived isotope with a half-life of 22 minutes. It is also the only known isotope of francium that occurs in nature. All 33 of francium’s isotopes are highly unstable.
Because all of francium’s known isotopes are highly unstable, knowledge of francium’s chemical elements is acquired through radioactive techniques. No weighable quantity of the element has been prepared or isolated.
Sources of francium
Natural francium is the result of an alpha disintegration of actinium. It occurs naturally in uranium minerals, but the Earth’s crust probably contains less than 1 ounce of francium at any time. Francium can be made artificially if thorium is bombarded with protons.
(Source: Jefferson Lab)