Editing Decay chain (section)

===Neptunium series===
[[Image:Decay Chain(4n+1, Neptunium Series).svg|300px|thumb|right]]
The 4n + 1 chain of neptunium-237 is commonly called the "neptunium series" or "neptunium cascade". In this series, only two of the isotopes involved are found naturally in significant quantities, namely the final two: bismuth-209 and thallium-205. Some of the other isotopes have been detected in nature, originating from trace quantities of <sup>237</sup>Np produced by the (n,2n) [[spallation|knockout]] reaction in primordial <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> A [[smoke detector]] containing an [[americium-241]] ionization chamber accumulates a significant amount of [[neptunium]]-237 as its americium decays. The following elements are also present in it, at least transiently, as decay products of the neptunium:  actinium, [[astatine]], bismuth, [[francium]], lead, polonium, [[protactinium]], radium, radon, thallium, thorium, and [[uranium]]. Since this series was only discovered and studied in 1947–1948,<ref name=th2>{{Thoennessen2016|pages=20}}</ref> its nuclides were never given historic names. One unique trait of this decay chain is that the noble gas radon is only produced in a rare branch (not shown in the illustration) but not the main decay sequence; thus, radon from this decay chain does not migrate through rock nearly as much as from the other three. Another unique trait of this decay sequence is that it ends in thallium (practically speaking, bismuth) rather than lead. This series terminates with the stable isotope thallium-205.

The total energy released from californium-249 to thallium-205, including the energy lost to [[neutrino]]s, is 66.8&nbsp;MeV.

{| class="wikitable" style="margin:auto; text-align:center;"
!Nuclide
!Decay mode
!Half-life<br />(''a'' = years)
!Energy released<br/>MeV
!Decay product
|-
|[[Californium-249|<sup>249</sup>Cf]]
|[[alpha decay|α]]
|351 a
|5.813+.388
|[[Curium-245|<sup>245</sup>Cm]]
|-
| <sup>245</sup>Cm
| α
| 8500 a
| 5.362+.175
| [[Plutonium-241|<sup>241</sup>Pu]]
|-
| <sup>241</sup>Pu
| [[beta decay|β<sup>−</sup>]]
| 14.4 a
| 0.021
| [[Americium-241|<sup>241</sup>Am]]
|-
| <sup>241</sup>Am
| α
| 432.7 a
| 5.638
| [[Neptunium-237|<sup>237</sup>Np]]
|-
| <sup>237</sup>Np
| α
| 2.14×10<sup>6</sup> a
| 4.959
| [[Protactinium-233|<sup>233</sup>Pa]]
|-
| <sup>233</sup>Pa
| β<sup>−</sup>
| 27.0 d
| 0.571
| [[Uranium-233|<sup>233</sup>U]]
|-
| <sup>233</sup>U
| α
| 1.592×10<sup>5</sup> a
| 4.909
| [[Thorium-229|<sup>229</sup>Th]]
|-
| <sup>229</sup>Th
| α
| 7340 a
| 5.168
| [[Radium-225|<sup>225</sup>Ra]]
|-
| <sup>225</sup>Ra
| β<sup>−</sup> 99.9974%<br />α 0.0026%
| 14.9 d
| 0.36<br />5.097
| [[Actinium-225|<sup>225</sup>Ac]]<br />[[Radon-221|<sup>221</sup>Rn]]
|-
| <sup>225</sup>Ac
| α
| 10.0 d
| 5.935
| [[Francium-221|<sup>221</sup>Fr]]
|-
| <sup>221</sup>Rn
| β<sup>−</sup> 78%<br />α 22%
| 25.7 min
| 1.194<br />6.163
| [[Francium-221|<sup>221</sup>Fr]]<br />[[Polonium-217|<sup>217</sup>Po]]
|-
| <sup>221</sup>Fr
| α 99.9952% <br /> β<sup>−</sup> 0.0048%
| 4.8 min
| 6.458<br /> 0.314
| [[Astatine-217|<sup>217</sup>At]]<br />[[Radium-221|<sup>221</sup>Ra]]
|-
| <sup>221</sup>Ra
| α
| 28 s
| 6.880
| [[Radon-217|<sup>217</sup>Rn]]
|-
| <sup>217</sup>Po
| α 97.5% <br /> β<sup>−</sup> 2.5%
|1.53 s
| 6.662<br />1.488
|[[Lead-213|<sup>213</sup>Pb]] <br /> [[Astatine-217|<sup>217</sup>At]]
|-
| <sup>217</sup>At
| α 99.992% <br /> β<sup>−</sup> 0.008%
|32 ms
| 7.201 <br /> 0.737
|[[Bismuth-213|<sup>213</sup>Bi]] <br /> [[Radon-217|<sup>217</sup>Rn]]
|-
| <sup>217</sup>Rn
|  α
| 540 μs
| 7.887
| [[Polonium-213|<sup>213</sup>Po]]
|-
| <sup>213</sup>Pb
|  β<sup>−</sup>
| 10.2 min
|2.028
| [[Bismuth-213|<sup>213</sup>Bi]]
|-
| <sup>213</sup>Bi
|  β<sup>−</sup> 97.80% <br />  α 2.20%
| 46.5 min
| 1.423 <br /> 5.87
| [[Polonium-213|<sup>213</sup>Po]] <br /> [[Thallium-209|<sup>209</sup>Tl]]
|-
| <sup>213</sup>Po
|  α
| 3.72 μs
| 8.536
| [[Lead|<sup>209</sup>Pb]]
|-
| <sup>209</sup>Tl
|  β<sup>−</sup>
| 2.2 min
| 3.99
| [[Lead-209|<sup>209</sup>Pb]]
|-
| <sup>209</sup>Pb
|  β<sup>−</sup>
| 3.25 h
| 0.644
| [[Bismuth-209|<sup>209</sup>Bi]]
|-
| <sup>209</sup>Bi
| α
| 2.01×10<sup>19</sup> a
| 3.137
| [[Thallium-205|<sup>205</sup>Tl]]
|-
| <sup>205</sup>Tl
| .
| stable
| .
| .
|}