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Seldom found in nature. | Atomic Number: | 87 | Atomic Symbol: | Fr | | Atomic Weight: | 223 | Electron Configuration: | 2-8-18-8-1 | | Shells: | 2,8,18,32,18,8,1 | Filling Orbital: | 7s1 | | Melting Point: | 27oC | Boiling Point: | 677oC | | Description: | Radioactive alkali metal. |
History(France) Discovered in 1939 by Mlle. Marguerite Perey of the
Curie Institute, Paris.
OccurenceFrancium, the heaviest known member of the alkali metals
series, occurs as a reult of an alpha disintegration of actinium. It can also be
made by artificially by bombarding thorium with protons. While it occurs
naturally in uranium minerals, there is probably less than an ounce of francium
at any time in the total crust of the earth. It has the highest equivalent
weight of any element, and is the most unstable of the first 101 elements of the
periodic system.
IsotopesThirty-three isotopes of francium are recognized. The longest
lived 223Fr (Ac, K), a daughter of 227Ac, has a half-lilfe of 22 min. This is
the only isotope of francium occurring in nature.
PropertiesBecause all known isotopes of francium are highly unstable,
knowledge of the chemical properties of this element comes from radiochemical
techniques. No weighable quantity of the element has been prepared or isolated.
The chemical properties of francium most resemble cesium.
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