Francium is a chemical element with the symbol Fr and atomic number 87.
It is extremely radioactive;
its most stable isotope, francium-223 , has a half-life of only 22 minutes.
It is the second-most electropositive element, behind only caesium, and is the second rarest naturally occurring element .
Francium's isotopes decay quickly into astatine, radium, and radon.
The electronic structure of a francium atom is 7s1;
thus, the element is classed as an alkali metal.
Bulk francium has never been seen.
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.
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.
Francium was discovered by Marguerite Perey in France in 1939.