Discovery date : 1939
Discovered by: Marguerite Perey
Origin of the name: Francium is named after France.
Allotropes :
~>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, and is the second rarest naturally occurring element.
| FACT BOX | |||
| Group | 1 | Melting point | 21°C, 70°F, 294 K |
| Period | 7 | Boiling point | 650°C, 1202°F, 923 K |
| Block | s | Density (g cm−3) | Unknown |
| Atomic number | 87 | Relative atomic mass | [223] |
| State at 20°C | Solid | Key isotopes | 223Fr |
| Electron configuration | [Rn] 7s1 | CAS number | 7440-73-5 |
| ChemSpider ID | 4886484 | ChemSpider is a free chemical structure database | |
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.