Atomic Number: 87
Atomic Weight: 223.0197
Discovery: Discovered in 1939 by Marguerite Perey of the Curie Institute, Paris (France).
Electron Configuration: [Rn] 7s1
Word Origin: Named for France, the country of its discoverer.
Isotopes: There are 33 known isotopes of francium. The longest lived is Fr-223, a daughter of Ac-227, with a half-life of 22 minutes. This is the only naturally-occuring isotope of francium.
Properties: The melting point of francium is 27 °C, boiling point is 677 °C, and its valence is 1. Francium is the heaviest known member of the alkali metals series. It has the highest equivalent weight of any element and is the most unstable of the first 101 elements of the periodic system. All known isotopes of francium are highly unstable, so knowledge of the chemical properties of this element comes from radiochemical techniques. No weighable quantity of the element has been prepared or isolated. The chemical properties of francium most closely resemble those of cesium.
Sources: Francium occurs as a result of an alpha disintegration of actinium. It can be produced by artificially bombarding thorium with protons. It occurs naturally in uranium minerals, but there is probably less than an ounce of francium at any time in the total crust of the earth.
Element Classification: alkali Metal
Melting Point (K): 300
Boiling Point (K): 950
Ionic Radius: 180 (+1e)
Fusion Heat (kJ/mol): 15.7
First Ionizing Energy (kJ/mol): ~375
Oxidation States: 1
Lattice Structure: Body-Centered Cubic
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)
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