All isotopes of francium decay into astatine, radium, or radon.

The only comparable element is astatine, whose most stable natural isotope, astatine-219 (the alpha daughter of francium-223), has a half-life of 56 seconds, although synthetic astatine-210 is much longer-lived with a half-life of 8.1 hours. Characteristics įrancium is one of the most unstable of the naturally occurring elements: its longest-lived isotope, francium-223, has a half-life of only 22 minutes. The largest amount produced in the laboratory was a cluster of more than 300,000 atoms. As little as 200–500 g exists at any given time throughout the Earth's crust aside from francium-223 and francium-221, its other isotopes are entirely synthetic. Outside the laboratory, francium is extremely rare, with trace amounts found in uranium ores, where the isotope francium-223 (in the family of uranium-235) continually forms and decays. It was the last element first discovered in nature, rather than by synthesis. Prior to its discovery, it was referred to as eka- caesium or ekacaesium because of its conjectured existence below caesium in the periodic table. Obtaining such a sample is highly improbable, since the extreme heat of decay resulting from its short half-life would immediately vaporize any viewable quantity of the element.įrancium was discovered by Marguerite Perey in France (from which the element takes its name) in 1939. Because of the general appearance of the other elements in its periodic table column, it is presumed that francium would appear as a highly reactive metal, if enough could be collected together to be viewed as a bulk solid or liquid. The electronic structure of a francium atom is 7s 1, and so the element is classed as an alkali metal.īulk francium has never been seen.

The isotopes of francium decay quickly into astatine, radium, and radon. It is the second-most electropositive element, behind only caesium, and is the second rarest naturally occurring element (after astatine). It is extremely radioactive its most stable isotope, francium-223 (originally called actinium K after the natural decay chain in which it appears), has a half-life of only 22 minutes.

Francium is a chemical element with the symbol Fr and atomic number 87.

Francium atomic radius