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Francium


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Seldom found in nature.
Atomic Number:87Atomic Symbol:Fr
Atomic Weight:223Electron Configuration:2-8-18-8-1
Shells:2,8,18,32,18,8,1Filling Orbital:7s1
Melting Point:27oCBoiling Point:677oC
Description:Radioactive alkali metal.

History

(France) Discovered in 1939 by Mlle. Marguerite Perey of the Curie Institute, Paris.

Occurence

Francium, 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.

Isotopes

Thirty-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.

Properties

Because 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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