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87. FranciumName: Francium
Francium occurs as a result of α disintegration of actinium. Francium is found in uranium minerals, and can be made artificially by bombarding thorium with protons. It is the most unstable of the first 101 elements. The longest lived isotope, 223Fr, a daughter of 227Ac, has a half-life of 22 minutes. This is the only isotope of francium occurring in nature, but at most there is only 20-30 g of the element present in the earth's crust at any one time. No weighable quantity of the element has been prepared or isolated. There are about 20 known isotopes. Even though it naturally occurs in uranium minerals, it has been estimated that there might be less than one ounce of francium in the crust of the earth at any one time. It is the most unstable element among the first 101 and has the highest equivalent weight of any element. This element, which was named for France, was discovered in 1939 by Marguerite Perey of the Curie Institute in Paris. Francium is the heaviest alkali metal and occurs as a result of actinium's alpha decay and can be artificially made by bombarding thorium with protons. No research team has produced a weighable quantity of francium nor has this element been prepared or isolated, and probably never will be. Chemically, the properties of francium are closest to those of caesium. Quick links
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