Francium (Fr): Atomic number: 87, Atomic mass: (233) g.mol -1, Electronegativity: 0.7, Density: unknown, Melting point: 27 °C, Boiling point: 677 °C, Vanderwaals radius: unknown, Ionic radius: unknown, Isotopes: 4, Electronic shell: [ Rn ] 7s1, Energy of first ionisation: 375 kJ.mol -1, Discovered by: Marguerite Perey in 1939. Francium is extremely rare. Because of this its chemical and physical properties are not known. It has been studied by radiochemical techniques, which show that its most stable state is the ion Fr+. Francium is the least electronegative of all the known elements. Applications: No use has been found for what little francium can be produced. Francium in the environment: Francium occurs naturally to a very limited extent in uranium minerals. Nevertheless it has been estimated that there might be from 340 to 550 grams of francium in the earth's crust at any one time. Francium is the second rarest element in the crust, after astatine.

 

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Francium (Fr): Atomic number: 87, Atomic mass: (233) g.mol -1, Electronegativity: 0.7, Density: unknown, Melting point: 27 °C, Boiling point: 677 °C, Vanderwaals radius: unknown, Ionic radius: unknown, Iso . . . View Full Definition

Federal Register (FR): Each federal working day, this federal document publishes current Presidential orders or directives, agency regulations, proposed agency rules, notices and other documents that are required . . . View Full Definition

Alkali Metal: The Group 1 elements, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr) react with cold water for form strongly alkaline hydroxide solutions, and are re . . . View Full Definition