From Academic Kids
|Name, Symbol, Number||Francium, Fr, 87|
|Group, Period, Block||1(IA), 7, s|
|Density, Hardness||1870 kg/m3, no data|
|Atomic weight||(223.0197307) amu|
|Atomic radius||no data|
|Covalent radius||no data|
|van der Waals radius||no data|
|e- 's per energy level||2, 8, 18, 32, 18, 8, 1|
|Oxidation states (Oxide)||1 (strong base)|
|Crystal structure||Cubic body centered|
|State of matter||solid|
|Melting point||300.2 K (80.53 ?F)|
|Boiling point||950 K (523.4 ?F)|
|Molar volume||no data|
|Heat of vaporization||no data|
|Heat of fusion||no data|
|Vapor pressure||no data|
|Speed of sound||no data|
|Electronegativity||0.7 (Pauling scale)|
|Specific heat capacity||no data|
|Electrical conductivity||3 106/m ohm|
|Thermal conductivity||15 W/(m*K)|
|1st ionization potential||380 kJ/mol|
|Most stable isotopes|
|SI units & STP are used except where noted.|
This element, which was named for France, was discovered in 1939 by Marguerite Perey of the Curie Institute in Paris. Francium is the heaviest alkali metal and occurs as a result of actinium's alpha decay and can be artificially made by bombarding thorium with protons.
Even though it naturally occurs in uranium minerals, it has been estimated that there might be less than 30 grams of francium in the crust of the earth at any one time. It is the most unstable element among the first 101 and has the highest equivalent weight of any element.
There are 41 known isotopes of francium. With a 22 minute half life, the longest lived isotope of this element is 223Fr which is a daughter isotope of 227At and is the only isotope of francium that occurs naturally. All known isotopes of francium are highly unstable, therefore knowledge of the properties of this element only comes from radiochemical procedures.
A small number of pictures of francium have been taken but only of at the most 200,000 atoms at a time. The pictures were taken by trapping the atoms and using a special fluorescent imaging camera.
- Los Alamos National Laboratory - Francium (http://periodic.lanl.gov/elements/87.html)