Francium is an extremely radioactive alkali metal; it is the second-least electronegative element.
Core Principles & Analysis
Marguerite Perey discovered francium in 1939 at the Curie Institute in Paris while purifying actinium, making it the last element found in nature rather than synthesized; she named it after France.
Its longest-lived isotope, francium-223, has a half-life of just 22 minutes, and less than about 30 grams of the element exist in Earth's crust at any moment.
Despite its scarcity, physicists laser-trap francium atoms at accelerator facilities such as TRIUMF to study atomic parity violation, because its heavy nucleus amplifies weak-force effects.