Francium (Fr), heaviest chemical element of Group 1 (Ia) in the periodic table, the alkali metal group. It exists only in short-lived radioactive forms. Natural francium cannot be isolated in visible, weighable amounts, for only 24.5 grams (0.86 ounce) occur at any time in the entire crust of Earth. The chemistry of francium can be studied only by methods designed for trace quantities. In all respects, its observed behaviour, including the oxidation state of +1, is that to be expected of an alkali element filling a place just below cesium in the periodic table of the elements. There is almost no information on its biological aspects. Continue reading from Encyclopedia Britannica
Mendeleev said there should be an element like caesium waiting to be discovered. Consequently, there were claims, denials, and counterclaims by scientists who said they had found it. During the 1920s and 30s, these claims were made on the basis of unexplained radioactivity in minerals, or new lines in their X-ray spectra, but all eventually turned out not to be evidence of element 87.
Francium was finally discovered in 1939 by Marguerite Perey at the Curie Institute in Paris. She had purified a sample of actinium free of all its known radioactive impurities and yet its radioactivity still indicated another element was present, and which she rightly deduced was the missing element 87. Others challenged her results too, and it was not until after World War II that she was accepted as the rightful discoverer in 1946. Continue reading from Royal Society of Chemistry
Francium is both the heaviest of the known alkali metals and the most unstable of the first 101 elements in the Periodic Table. Because all of francium’s known isotopes are highly unstable, knowledge of francium’s chemical elements is acquired through radioactive techniques. 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. Continue reading from Live Science
