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Francium-223 is the most stable isotope, with a half-life of 21.8 minutes, [8] and it is highly unlikely that an isotope of francium with a longer half-life will ever be discovered or synthesized. [22] Francium-223 is a fifth product of the uranium-235 decay series as a daughter isotope of actinium-227; thorium-227 is the more common daughter. [23]
[3] [7] Francium is the second rarest element (after astatine) — only about 550g exists in the entire Earth's crust at any given time — and it was the last element to be discovered in nature. [5] [6] (Five elements that were discovered synthetically were later found to exist in nature: technetium, promethium, astatine, neptunium, and ...
Francium was the last element discovered in nature, rather than synthesized. Outside the laboratory, francium is extremely rare, with trace amounts found in uranium and thorium ores, where the isotope francium-223 is continually formed and continually decays.
Francium-223, the only naturally occurring isotope of francium, [57] [58] is the product of the alpha decay of actinium-227 and can be found in trace amounts in uranium minerals. [59] In a given sample of uranium, there is estimated to be only one francium atom for every 10 18 uranium atoms.
Francium was discovered by Marguerite Perey in France (from which the element takes its name) in 1939. [8] It was the last element discovered in nature, rather than by synthesis. [note 2] Outside the laboratory, francium is extremely rare, with trace amounts found in uranium and thorium ores, where the isotope francium-223 continually forms and ...
This list of chemical elements named after places includes elements named both directly and indirectly for places. 41 of the 118 chemical elements have names associated with, or specifically named for, places around the world or among astronomical objects.
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Francium (87 Fr) has no stable isotopes, thus a standard atomic weight cannot be given. Its most stable isotope is 223 Fr with a half-life of 22 minutes, occurring in trace quantities in nature as an intermediate decay product of 235 U. Of elements whose most stable isotopes have been identified with certainty, francium is the most unstable.