| Symbol | Fr |
| Atomnummer | 87 |
| Gruppe | 1 (Alkalimetaller) |
| Periode | 7 |
| Blok | s |
| Klassifikation | Alkalimetaller |
| Udseende | - |
| Farve | Sølv |
| Antal protoner | 87 p+ |
| Antal neutroner | 136 n0 |
| Antal elektroner | 87 e- |
| Fase ved STP | Fast |
| Massefylde | 1.87 g/cm3 |
| Atommasse | 223 u |
| Smeltepunkt | 300 K 26.85 °C 80.33 °F |
| Kogepunkt | 950 K 676.85 °C 1250.33 °F |
| Fordampningsvarme | 64 kJ/mol |
| Elektronegativitet (Pauling Scale) | 0.79 |
| Elektronaffinitet | 46.89 kJ/mol |
| Oxidationstrin | +1 (a strongly basic oxide) |
| Ioniseringsenergier |
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| Opdagelse og første isolation | Marguerite Perey (1939) |
Opdagelse af francium Francium was discovered by Marguerite Perey in France (from which the element takes its name) in 1939. Prior to its discovery, it was referred to as eka-caesium or ekacaesium because of its conjectured existence below caesium in the periodic table. It was the last element discovered in nature, rather than synthesized, following hafnium and rhenium. Perey named the new isotope actinium-K (it is now referred to as francium-223) and in 1946, she proposed the name catium (Cm) for her newly discovered element, as she believed it to be the most electropositive cation of the elements. Irène Joliot-Curie, one of Perey's supervisors, opposed the name due to its connotation of cat rather than cation; furthermore, the symbol coincided with that which had since been assigned to curium. Perey then suggested francium, after France. This name was officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) in 1949, becoming the second element after gallium to be named after France. It was assigned the symbol Fa, but this abbreviation was revised to the current Fr shortly thereafter. | |