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Francium is extremely rare. Because of this, its chemical and physical properties are not well characterized. It has been studied by radiochemical techniques, which show that its most stable state is the ion Fr+. Francium is the least electrone

역사The name derives from the country “France”, where the French physicist Marguerite Perey from the Curie Institute in Paris, France discovered it in 1939 in the alpha particle decay of actinium, 227Ac→4 He →223Fr, which was known as actinium-K and has a half-life of 22 minutes. An earlier claim of discovery in 1930 with the element name Virginium was determined to be incorrect. A similar claim for discovery of the element with atomic number 87 and named moldavium was also determined to be incorrect. The longest half-life associated with this unstable element is 22 minute 223Fr. 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.