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Figure. 1. Neutral francium atoms can be trapped in the MOT using a magnetic field and laser beams.[30]
6. Isotopes
There are 34 known isotopes of francium ranging in atomic mass from 199 to 232.[3] Francium has seven metastable nuclear isomers.[3] Francium-223 and francium-221 are the only isotopes that occur in nature, though the former is far more common.[33]
Francium-223 is the most stable isotope with a half-life of 21.8 minutes,[3] and it is highly unlikely that an isotope of francium with a longer half-life will ever be discovered or synthesized.[26] Francium-223 is the fifth product of the actinium decay series as the daughter isotope of actinium-227.[17] Francium-223 then decays into radium-223 by beta decay (1149 keV decay energy), with a minor (0.006%) alpha decay path to astatine-219 (5.4 MeV decay energy).[34]
Francium-221 has a half-life of 4.8 minutes.[3] It is the ninth product of the neptunium decay series as a daughter isotope of actinium-225.[17] Francium-221 then decays into astatine-217 by alpha decay (6.457 MeV decay energy).[3]
The least stable ground state isotope is francium-215, with a half-life of 0.12 μs. (9.54 MeV alpha decay to astatine-211):[3] Its metastable isomer, francium-215m, is less stable still, with a half-life of only 3.5 ns.[35]
7. Conclusion
As an individual representative of the periodic table of chemical elements Dmitry Ivanovich Mendeleyev, the element has unique chemical and physical properties
Element is of great economic importance and plays a major role in world culture
8. References
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Actually the least unstable isotope, Fr-223
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Some synthetic elements, like technetium, have later been found in nature.
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a b c d e Adloff, Jean-Pierre; Kaufman, George B. (2005-09-25). Francium (Atomic Number 87), the Last Discovered Natural Element. The Chemical Educator 10 (5). Retrieved on 2007-03-26.
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a b c d e Fontani, Marco (2005-09-10). "The Twilight of the Naturally-Occurring Elements: Moldavium (Ml), Sequanium (Sq) and Dor (Do)". International Conference on the History of Chemistry. Lisbon. pp. 1–8. Archived from the original on 2006-02-24.
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a b c d Van der Krogt, Peter (2006-01-10). "Francium". Elementymology & Elements Multidict. http://www.vanderkroft.net/elements/elem/fr.html. Retrieved 2007-04-08.
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MacPherson, H. G. (1934). "An Investigation of the Magneto-Optic Method of Chemical Analysis". Physical Review (American Physical Society) 47 (4): 310–315. doi:10.1103/PhysRev.47.310.
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"Francium". Los Alamos National Laboratory Chemistry Division. 2003-12-15. http://periodic.lanl.gov/elements/87.html. Retrieved 2007-03-29.
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