Francium
![Marguerite Perey, the discoverer of francium.](/Images/godic/202502/08/Marguerite_Perey1747.jpg")
![This sample of uraninite contains about 100,000 atoms (3.3×10−20 g) of francium-223 at any given time.[22]](/Images/godic/202502/08/Pichblende1747.jpg")
![Neutral francium atoms can be trapped in the MOT using a magnetic field and laser beams.[35]](/Images/godic/202502/08/Franciumtrap1748.PNG")
![Image of light emitted by a sample of 200,000 francium atoms in a magneto-optical trapHeat image of 300,000 francium atoms in a magneto-optical trap](/Images/godic/202502/08/Francium1748.jpg")
Francium is a chemical element with symbol Fr and atomic number 87. It used to be known as eka-caesium and actinium K. It is the second-least electronegative element, behind only caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon. As an alkali metal, it has one valence electron.