Editing Francium (section)

==Isotopes==
{{main|Isotopes of francium}}

There are 37 known isotopes of francium ranging in [[atomic mass]] from 197 to 233.{{NUBASE2020|ref}} Francium has seven [[metastability|metastable]] [[nuclear isomer]]s.<ref name="CRC2006" /> Francium-223 and francium-221 are the only isotopes that occur in nature, with the former being far more common.<ref name="nostrand679">{{cite book|date = 2005|title= Francium, in Van Nostrand's Encyclopedia of Chemistry|editor-last = Considine| editor-first = Glenn D.| page= 679|location= New York| publisher = Wiley-Interscience| isbn = 978-0-471-61525-5}}</ref>

Francium-223 is the most stable isotope, with a half-life of 21.8&nbsp;minutes,<ref name="CRC2006" /> and it is highly unlikely that an isotope of francium with a longer half-life will ever be discovered or synthesized.<ref name="mcgraw" /> 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.<ref name="nostrand332">{{cite book|date = 2005|title= Chemical Elements, in Van Nostrand's Encyclopedia of Chemistry|editor-last = Considine| editor-first = Glenn D.|page=332|location= New York| publisher = Wiley-Interscience| isbn = 978-0-471-61525-5}}</ref> Francium-223 then decays into radium-223 by [[beta decay]] (1.149&nbsp;MeV [[decay energy]]), with a minor (0.006%) [[alpha decay]] path to astatine-219 (5.4&nbsp;MeV decay energy).<ref>{{cite web |author=National Nuclear Data Center |date=1990 |title=Table of Isotopes decay data |url=http://ie.lbl.gov/toi/nuclide.asp?iZA=870223 |publisher=[[Brookhaven National Laboratory]] |access-date=April 4, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20061031212436/http://ie.lbl.gov/toi/nuclide.asp?iZA=870223 |archive-date=October 31, 2006}}</ref>

Francium-221 has a half-life of 4.8&nbsp;minutes.<ref name="CRC2006" /> It is the ninth product of the [[neptunium]] decay series as a daughter isotope of [[actinium-225]].<ref name="nostrand332" /> Francium-221 then decays into astatine-217 by alpha decay (6.457&nbsp;MeV decay energy).<ref name="CRC2006" /> Although all primordial <sup>237</sup>Np is [[extinct radionuclide|extinct]], the neptunium decay series continues to exist naturally in tiny traces due to (n,2n) knockout reactions in natural <sup>238</sup>U.<ref name=4n1>{{cite journal |last1=Peppard |first1=D. F. |last2=Mason |first2=G. W. |last3=Gray |first3=P. R. |last4=Mech |first4=J. F. |title=Occurrence of the (4n + 1) series in nature |journal=Journal of the American Chemical Society |date=1952 |volume=74 |issue=23 |pages=6081–6084 |doi=10.1021/ja01143a074 |bibcode=1952JAChS..74.6081P |url=https://digital.library.unt.edu/ark:/67531/metadc172698/m2/1/high_res_d/metadc172698.pdf }}</ref> Francium-222, with a half-life of 14&nbsp;minutes, may be produced as a result of the beta decay of natural [[radon-222]]; this process has nonetheless not yet been observed,<ref name="bellidecay">{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Danevich |first3=F. A. |last4=Incicchitti |first4=A. |last5=Tretyak |first5=V. I. |display-authors=3 |title=Experimental searches for rare alpha and beta decays |journal=European Physical Journal A |date=2019 |volume=55 |issue=8 |pages=140–1–140–7 |doi=10.1140/epja/i2019-12823-2 |issn=1434-601X |arxiv=1908.11458|bibcode=2019EPJA...55..140B |s2cid=201664098 }}</ref> and it is unknown whether this process is energetically possible.{{NoteTag|AME2020 gives <sup>222</sup>Rn a lower mass than <sup>222</sup>Fr,{{AME2020 II|ref}} which would forbid single beta decay, though it is possible within the given error margin and is explicitly predicted by Belli et al.<ref name=BelliBaF2>{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Cappella |first3=C. |last4=Caracciolo |first4=V. |last5=Cerulli |first5=R. |last6=Danevich |first6=F.A. |last7=Di Marco |first7=A. |last8=Incicchitti |first8=A. |last9=Poda |first9=D.V. |last10=Polischuk |first10=O.G. |last11=Tretyak |first11=V.I. |title=Investigation of rare nuclear decays with BaF<sub>2</sub> crystal scintillator contaminated by radium |date=2014 |journal=European Physical Journal A |volume=50 |issue=9 |pages=134–143 |doi=10.1140/epja/i2014-14134-6 |arxiv=1407.5844|bibcode=2014EPJA...50..134B |s2cid=118513731 }}</ref>}}

The least stable [[ground state]] isotope is francium-215, with a half-life of 90&nbsp;ns:{{NUBASE2020|ref}} it undergoes a 9.54&nbsp;MeV alpha decay to astatine-211.<ref name="CRC2006" />