Although the easier ionization of radon leads one to expect the most extensive chemistry for that element, the high instability of even the most stable isotope has severely limited studies of it.

氡容易离子化，这让人期望，该元素有最广泛的化学反应，但是，这个元素最稳定的同位素也极不稳定，这使氡的研究受到了严重的约束。

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Even Francium's most stable isotope, Francium-223 only has a half-life of 22 minutes.

钫的最稳定的同位素，钫- 223也只有22分钟的半衰期。

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And this whole topic completely ignores the other, even rarer form of Heliem, the Isotope Helium3, which is formed only as a biproduct of the radioactive decay of the Tritium used in making nuclear missiles.

FORBES: What Great Helium Shortage?

If enacted in its current form, Section 621 of this year's Energy bill , by contrast, would allow foreign companies to receive U.S. HEU for use in medical isotope production without having to move toward a low-enriched uranium (LEU) target, even if it is technically feasible for them to do so.

CENTERFORSECURITYPOLICY: Kyl and Schumer move to monitor uranium exports