The Online Encyclopedia and Dictionary







francium - radium

Name, Symbol, Number Francium, Fr, 87
Series Alkali metals
Group, Period, Block 1(IA), 7, s
Density, Hardness 1870 kg/m3, no data
Appearance metallic
Atomic properties
Atomic weight (223.0197307) amu
Atomic radius no data
Covalent radius no data
van der Waals radius no data
Electron configuration [Rn]7s1
e- 's per energy level 2, 8, 18, 32, 18, 8, 1
Oxidation states (Oxide) 1 (strong base)
Crystal structure Cubic body centered
Physical properties
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
iso NA half-life DM DE MeV DP
222Fr {syn.} 14.2 m - 2.033 222Ra
223Fr 100% 22.00 m -
SI units & STP are used except where noted.

Francium is a chemical element in the periodic table that has the symbol Fr and atomic number 87. This is a highly radioactive alkali metal that is found in uranium and thorium ores.

Notable characteristics

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.


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Last updated: 08-02-2005 02:59:06
Last updated: 09-12-2005 02:39:13