View source for Decay chain

{{Short description|Series of radioactive decays}}
{{Nuclear physics}}

In [[nuclear science]] a '''decay chain''' refers to the predictable series of [[radioactive decay|radioactive disintegration]]s undergone by the nuclei of certain unstable chemical elements. 

[[Radionuclide|Radioactive isotopes]] do not usually decay directly to [[stable isotopes]], but rather into another radioisotope. The isotope produced by this radioactive emission then decays into another, often radioactive isotope. This chain of decays always terminates in a [[Stable nuclide|stable isotope]], whose nucleus no longer has the surplus of energy necessary to produce another emission of radiation. Such stable isotopes may be said to have  reached their ''[[Ground state|ground states]]''.

The stages or steps in a decay chain are referred to by their relationship to previous or subsequent stages. Hence, a ''parent isotope'' is one that undergoes decay to form a ''daughter isotope''. For example element 92, [[uranium]], has an isotope with 144 neutrons ([[Uranium-236|<sup>236</sup>U]]) and it decays into an isotope of element 90, [[thorium]], with 142 neutrons ([[Isotopes of thorium|<sup>232</sup>Th]]). The daughter isotope may be stable or it may itself decay to form another daughter isotope.  <sup>232</sup>Th does this when it decays into [[Isotopes of radium|radium-228]]. The daughter of a daughter isotope, such as  <sup>228</sup>Ra, is sometimes called a ''granddaughter isotope''.

The time required for an atom of a parent isotope to decay into its daughter is fundamentally unpredictable and varies widely. For individual nuclei the process is [[Uncertainty principle|not known to have determinable causes]] and the time at which it occurs is therefore [[Poisson point process|completely random]]. The only prediction that can be made is statistical and expresses an average rate of decay. This rate can be represented by adjusting the curve of a decaying [[exponential distribution]] with a [[decay constant]] (''λ'') particular to the isotope. On this understanding the radioactive decay of an initial population of unstable atoms over time ''t'' follows the curve given by ''[[E (mathematical constant)|e]]''<sup>−''λt''</sup>.

One of the most important properties of any radioactive material follows from this analysis, its [[half-life]]. This refers to the time required for half of a given number of radioactive atoms to decay and is inversely related to the isotope's decay constant, ''λ''. Half-lives have been determined in laboratories for many radionuclides, and can [[List of radioactive nuclides by half-life|range]] from nearly instantaneous—[[Isotopes of hydrogen|hydrogen-5]] decays in less [[Speed of light|time than it takes]] for a photon to go from one end of its nucleus to the other—to fourteen [[Orders of magnitude (time)|orders of magnitude]] longer than the [[age of the universe]]: [[Isotopes of tellurium|tellurium-128]] has a half-life of {{val|2.2|e=24|u=years}}.

[[File:DecayChain241Pu-eng.svg|thumb|Quantity calculation with the Bateman-Function for <sup>241</sup>Pu]]
The [[Bateman equation]] predicts the relative quantities of all the isotopes that compose a given decay chain once that decay chain has proceeded long enough for some of its daughter products to have reached the stable (i.e., nonradioactive) end of the chain. A decay chain that has reached this state, which may require billions of years, is said to be in ''equilibrium''. A sample of radioactive material in ''equilibrium'' produces a steady and steadily decreasing quantity of radioactivity as the isotopes that compose it traverse the decay chain. On the other hand, if a sample of radioactive material has been isotopically enriched, meaning that a radioisotope is present in larger quantities than would exist if a decay chain were the only cause of its presence, that sample is said to be ''out of equilibrium''. An unintuitive consequence of this disequilibrium is that a sample of [[Nuclear enrichment|enriched]] material may occasionally increase in radioactivity as daughter products that are more highly radioactive than their parents accumulate. Both [[Enriched uranium|enriched]] and [[Depleted uranium|depleted]] uranium provide examples of this phenomenon.

== History ==
The chemical elements came into being in two phases. The first commenced shortly after the [[Big Bang]]. From ten seconds to 20 minutes after the beginning of the universe the [[Big Bang nucleosynthesis|earliest condensation of light atoms]] was responsible for the manufacture of the four lightest elements. The vast majority of this primordial production consisted of the three lightest isotopes of [[hydrogen]]—[[Isotopes of hydrogen|protium]], [[deuterium]] and [[tritium]]—and two of the nine known isotopes of [[helium]]—[[helium-3]] and [[helium-4]]. Trace amounts of [[Isotopes of lithium#Lithium-7|lithium-7]] and [[Isotopes of beryllium#Beryllium-7|beryllium-7]] were likely also produced. 

So far as is known, all heavier elements came into being starting around 100 million years later, in a second phase of [[nucleosynthesis]] that commenced with the birth of the [[Primordial star|first stars]].<ref>{{Cite web |last=Bromm |first=Richard B. Larson, Volker |title=The First Stars in the Universe |url=https://www.scientificamerican.com/article/the-first-stars-in-the-un/ |access-date=2024-09-29 |website=Scientific American |language=en}}</ref> The nuclear furnaces that power stellar evolution were necessary to create large quantities of all elements heavier than helium, and the [[R-process|r-]] and [[s-process]]<nowiki/>es of neutron capture that occur in stellar cores are thought to have created all such elements up to [[iron]] and [[nickel]] (atomic numbers 26 and 28). The [[Supernova nucleosynthesis|extreme conditions]] that attend [[Supernova|supernovae]] explosions are capable of creating the elements between [[oxygen]] and [[rubidium]] (i.e., atomic numbers 8 through 37). The creation of heavier elements, including those without stable isotopes—all elements with atomic numbers greater than lead's, 82—appears to rely on r-process nucleosynthesis operating amid the immense concentrations of free neutrons released during [[Neutron star merger|neutron star mergers]].

Most of the isotopes of each chemical element present in the Earth today were formed by such processes no later than the time of [[History of Earth|our planet's condensation]] from the solar [[Protoplanetary disk|protoplanetary disc]], around 4.5 billion years ago. The exceptions to these so-called ''primordial'' elements are those that have resulted from the radioactive disintegration of unstable parent nuclei as they progress down one of several decay chains, each of which terminates with the production of one of the 251 stable isotopes known to exist. Aside from cosmic or stellar nucleosynthesis, and decay chains the only other ways of producing a chemical element rely on [[Nuclear weapon|atomic weapons]], nuclear reactors ([[Natural nuclear fission reactor|natural]] or [[Nuclear reactor|manmade]]) or the laborious atom-by-atom [[Superheavy element|assembly]] of nuclei with [[Particle accelerator|particle accelerators]].

Unstable isotopes decay to their daughter products (which may sometimes be even more unstable) at a given rate; eventually, often after a series of decays, a stable isotope is reached: there are 251 stable isotopes in the universe. In stable isotopes, light elements typically have a lower ratio of neutrons to protons in their nucleus than heavier elements. Light elements such as [[helium-4]] have close to a 1:1 neutron:proton ratio. The heaviest elements such as uranium have close to 1.5 neutrons per proton (e.g. 1.587 in [[uranium-238]]). No nuclide heavier than lead-208 is stable; these heavier elements have to shed mass to achieve stability, mostly by [[alpha decay]]. The other common way for isotopes with a high neutron to proton ratio (n/p) to decay is [[beta decay]], in which the nuclide changes elemental identity while keeping the same mass number and lowering its n/p ratio. For some isotopes with a relatively low n/p ratio, there is an [[positron emission|inverse beta decay]], by which a proton is transformed into a neutron, thus moving towards a stable isotope; however, since fission almost always produces products which are neutron heavy, [[positron emission]] or [[electron capture]] are rare compared to electron emission. There are many relatively short beta decay chains, at least two (a heavy, beta decay and a light, [[positron]] decay) for every discrete weight up to around 207 and some beyond, but for the higher mass elements (isotopes heavier than lead) there are only four pathways which encompass all decay chains.{{Citation needed|date=July 2023}} This is because there are just two main decay methods: [[alpha radiation]], which reduces the mass by 4 [[atomic mass units]] (amu), and beta, which does not change the mass number (just the atomic number and the p/n ratio). The four paths are termed 4n, 4n&nbsp;+&nbsp;1, 4n&nbsp;+&nbsp;2, and 4n&nbsp;+&nbsp;3; the remainder from dividing the atomic mass by four gives the chain the isotope will use to decay. There are other decay modes, but they invariably occur at a lower probability than alpha or beta decay. (It should not be supposed that these chains have no branches: the diagram below shows a few branches of chains, and in reality there are many more, because there are many more isotopes possible than are shown in the diagram.) For example, the third atom of [[nihonium-278]] synthesised underwent six alpha decays down to [[mendelevium-254]],<ref name="six-alpha" /> followed by an [[electron capture]] (a form of beta decay) to [[fermium-254]],<ref name="six-alpha" /> and then a seventh alpha to [[californium-250]],<ref name="six-alpha">{{cite journal|journal=Journal of the Physical Society of Japan|volume=81|pages=103201 |date=2012|title=New Results in the Production and Decay of an Isotope, <sup>278</sup>113, of the 113th Element|author=K. Morita|doi=10.1143/JPSJ.81.103201|last2=Morimoto|first2=Kouji|last3=Kaji|first3=Daiya|last4=Haba|first4=Hiromitsu|last5=Ozeki|first5=Kazutaka|last6=Kudou|first6=Yuki|last7=Sumita|first7=Takayuki|last8=Wakabayashi|first8=Yasuo|last9=Yoneda|first9=Akira|first10=Kengo |last10=Tanaka|first11=Sayaka |last11=Yamaki|first12=Ryutaro |last12=Sakai|first13=Takahiro |last13=Akiyama|first14=Shin-ichi |last14=Goto|first15=Hiroo |last15=Hasebe|first16=Minghui |last16=Huang|first17=Tianheng |last17=Huang|first18=Eiji |last18=Ideguchi|first19=Yoshitaka |last19=Kasamatsu|first20=Kenji |last20=Katori|first21=Yoshiki |last21=Kariya|first22=Hidetoshi |last22=Kikunaga|first23=Hiroyuki |last23=Koura|first24=Hisaaki |last24=Kudo|first25=Akihiro |last25=Mashiko|first26=Keita |last26=Mayama|first27=Shin-ichi |last27=Mitsuoka|first28=Toru |last28=Moriya|first29=Masashi |last29=Murakami|first30=Hirohumi |last30=Murayama|first31=Saori |last31=Namai|first32=Akira |last32=Ozawa|first33=Nozomi |last33=Sato|first34=Keisuke |last34=Sueki|first35=Mirei |last35=Takeyama|first36=Fuyuki |last36=Tokanai|first37=Takayuki |last37=Yamaguchi|first38=Atsushi |last38=Yoshida
|issue=10|display-authors=10|arxiv = 1209.6431 |bibcode = 2012JPSJ...81j3201M |s2cid=119217928 }}</ref> upon which it would have followed the 4n&nbsp;+&nbsp;2 chain (radium series) as given in this article. However, the heaviest [[superheavy element|superheavy]] nuclides synthesised do not reach the four decay chains, because they reach a [[spontaneous fission|spontaneously fissioning]] nuclide after a few alpha decays that terminates the chain: this is what happened to the first two atoms of nihonium-278 synthesised,<ref name="Nh278 04Mo01">{{cite journal|title=Experiment on the Synthesis of Element 113 in the Reaction <sup>209</sup>Bi(<sup>70</sup>Zn, n)<sup>278</sup>113|doi=10.1143/JPSJ.73.2593|year=2004|last1=Morita |first1=Kosuke |journal=Journal of the Physical Society of Japan |volume=73 |pages=2593–2596 |last2=Morimoto |first2=Kouji |last3=Kaji |first3=Daiya |last4=Akiyama |first4=Takahiro |last5=Goto |first5=Sin-Ichi |last6=Haba |first6=Hiromitsu |last7=Ideguchi |first7=Eiji |last8=Kanungo |first8=Rituparna |last9=Katori |first9=Kenji |last10=Koura |first10=Hiroyuki |last11=Kudo |first11=Hisaaki |last12=Ohnishi |first12=Tetsuya |last13=Ozawa |first13=Akira |last14=Suda |first14=Toshimi |last15=Sueki |first15=Keisuke |last16=Xu |first16=Hushan |last17=Yamaguchi |first17=Takayuki |last18=Yoneda |first18=Akira |last19=Yoshida |first19=Atsushi |last20=Zhao |first20=Yuliang |display-authors=8 |issue=10 |bibcode = 2004JPSJ...73.2593M |doi-access= }}</ref><ref name="JWP Nh278">{{cite journal |last1=Barber |first1=Robert C. |last2=Karol |first2=Paul J |last3=Nakahara |first3=Hiromichi |last4=Vardaci |first4=Emanuele |last5=Vogt |first5=Erich W. |title=Discovery of the elements with atomic numbers greater than or equal to 113 (IUPAC Technical Report)|doi=10.1351/PAC-REP-10-05-01 |journal=Pure and Applied Chemistry |year=2011 |volume=83|issue=7 |page=1485|doi-access=free }}</ref> as well as to all heavier nuclides produced.

Three of those chains have a long-lived isotope (or nuclide) near the top; this long-lived nuclide is a bottleneck in the process through which the chain flows very slowly, and keeps the chain below them "alive" with flow. The three long-lived nuclides are uranium-238 (half-life 4.5 billion years), uranium-235 (half-life 700 million years) and thorium-232 (half-life 14 billion years). The fourth chain has no such long-lasting bottleneck nuclide near the top, so almost all of the nuclides in that chain have long since decayed down to just before the end: bismuth-209. This nuclide was long thought to be stable, but in 2003 it was found to be unstable, with a very long half-life of 20.1 billion billion years;<ref>{{Cite journal|author=J.W. Beeman|display-authors=et al|date=2012|title=First Measurement of the Partial Widths of <sup>209</sup>Bi Decay to the Ground and to the First Excited States|journal=Physical Review Letters |volume=108 |issue=6 |pages=062501|doi=10.1103/PhysRevLett.108.062501|pmid=22401058|arxiv=1110.3138|s2cid=118686992 }}</ref> it is the last step in the chain before stable thallium-205. Because this bottleneck is so long-lived, very small quantities of the final decay product have been produced, and for most practical purposes bismuth-209 is the final decay product.

In the distant past, during the first few million years of the history of the Solar System, there were more kinds of unstable high-mass nuclides in existence, and the four chains were longer, as they included nuclides that have since decayed away. Notably, <sup>244</sup>Pu, <sup>237</sup>Np, and <sup>247</sup>Cm have half-lives over a million years and would have then been lesser bottlenecks high in the 4n, 4n+1, and 4n+3 chains respectively.<ref name=Davis>{{cite journal |last1=Davis |first1=Andrew M. |date=2022 |title=Short-Lived Nuclides in the Early Solar System: Abundances, Origins, and Applications |journal=Annual Review of Nuclear and Particle Science |volume=72 |issue= |pages=339–363 |doi=10.1146/annurev-nucl-010722-074615 |doi-access=free |bibcode=2022ARNPS..72..339D }}</ref> (There is no nuclide with a half-life over a million years above <sup>238</sup>U in the 4n+2 chain.) Today some of these formerly extinct isotopes are again in existence as they have been manufactured. Thus they again take their places in the chain: plutonium-239, used in nuclear weapons, is the major example, decaying to uranium-235 via alpha emission with a half-life 24,500 years. There has also been large-scale production of neptunium-237, which has resurrected the hitherto extinct fourth chain.<ref>{{cite book|last1=Koch|first1=Lothar|title=Transuranium Elements, in Ullmann's Encyclopedia of Industrial Chemistry|publisher=Wiley|date=2000|doi=10.1002/14356007.a27_167}}</ref> The tables below hence start the four decay chains at isotopes of [[californium]] with mass numbers from 249 to 252.

{|class=wikitable
|+Summary of the four decay chain pathways
|'''Name of series'''||Thorium||Neptunium||Uranium||Actinium
|-
|'''Mass numbers'''||4''n''||4''n''+1||4''n''+2||4''n''+3
|-
|'''Long-lived nuclide'''||<sup>232</sup>Th<br>(<sup>244</sup>Pu)||<sup>209</sup>Bi<br>(<sup>237</sup>Np)||<sup>238</sup>U<br>&nbsp;||<sup>235</sup>U<br>(<sup>247</sup>Cm)
|-
|'''Half-life'''<br/>(billions of years)||14<br>(0.08)|| {{val|20100000000}}<br>(0.00214) ||4.5<br>&nbsp;||0.7<br>(0.0156)
|-
|'''End of chain'''||<sup>208</sup>Pb||<sup>205</sup>Tl||<sup>206</sup>Pb||<sup>207</sup>Pb
|}

These four chains are summarised in the chart in the following section.

== Types of decay ==
[[Image:Radioactive decay chains diagram.svg|thumb|right|350px| This diagram illustrates the four decay chains discussed in the text: thorium (4n, in blue), neptunium (4n+1, in pink), radium (4n+2, in red) and actinium (4n+3, in green).]] The four most common modes of radioactive decay are: alpha decay, beta decay, [[inverse beta decay]] (considered as both positron emission and electron capture), and [[isomeric transition]].  Of these decay processes, only alpha decay (fission of a [[helium-4]] nucleus) changes the [[atomic mass]] number (''A'') of the nucleus, and always decreases it by four. Because of this, almost any decay will result in a nucleus whose atomic mass number has the same [[modular arithmetic|residue]] mod 4. This divides the list of nuclides into four classes. All the members of any possible decay chain must be drawn entirely from one of these classes.

Three main decay chains (or families) are observed in nature. These are commonly called the thorium series, the radium or uranium series, and the [[actinium]] series, representing three of these four classes, and ending in three different, stable isotopes of [[lead]]. The mass number of every isotope in these chains can be represented as ''A''&nbsp;=&nbsp;4''n'', ''A''&nbsp;=&nbsp;4''n''&nbsp;+&nbsp;2, and A&nbsp;=&nbsp;4''n''&nbsp;+&nbsp;3, respectively. The long-lived starting isotopes of these three isotopes, respectively [[thorium-232]], [[uranium-238]], and [[uranium-235]], have existed since the formation of the Earth, ignoring the artificial isotopes and their decays created since the 1940s.

Due to the relatively short [[half-life]] of its starting isotope [[neptunium-237]] (2.14 million years), the fourth chain, the [[neptunium]] series with ''A''&nbsp;=&nbsp;4''n''&nbsp;+&nbsp;1, is already extinct in nature, except for the final rate-limiting step, decay of [[bismuth-209]]. Traces of <sup>237</sup>Np and its decay products do occur in nature, however, as a result of neutron reactions in uranium ore; neutron capture by natural thorium to give <sup>233</sup>U is also possible.<ref name=4n1/> The ending isotope of this chain is now known to be [[thallium-205]]. Some older sources give the final isotope as bismuth-209, but in 2003 it was discovered that it is very slightly radioactive, with a half-life of {{val|2.01|e=19|u=years}}.<ref name=nubase>{{NUBASE2016}}</ref>

There are also non-transuranic decay chains of unstable isotopes of light elements, for example those of [[magnesium-28]] and [[chlorine-39]]. On Earth, most of the starting isotopes of these chains before 1945 were generated by [[cosmic radiation]]. Since 1945, the testing and use of nuclear weapons has also released numerous radioactive [[fission products]]. Almost all such isotopes decay by either β<sup>−</sup> or β<sup>+</sup> decay modes, changing from one element to another without changing atomic mass. These later daughter products, being closer to stability, generally have longer half-lives until they finally reach stability.

== Heavy nuclei (actinide) decay chains ==
{{Actinidesvsfissionproducts}}
In the four tables below, the minor branches of decay (with the branching probability of less than 0.0001%) are omitted. The energy release includes the total kinetic energy of all the emitted particles ([[electron]]s, [[alpha particle]]s, [[Gamma rays|gamma quanta]], [[neutrino]]s, [[Auger electron]]s and [[X-ray]]s) and the recoil nucleus, assuming that the original nucleus was at rest. The letter 'a' represents a year (from the Latin ''[[:wikt:annus|annus]]'').

In the tables below (except neptunium), the historic names of the naturally occurring nuclides are also given. Such names were used at the time when the decay chains were first discovered and investigated; the system listed was only finalized in the 1920s but it would be too confusing to give earlier names also. From these historical names one can thus find the modern isotopic designation.

The three naturally-occurring actinide alpha decay chains given below—thorium, uranium/radium (from uranium-238), and actinium (from uranium-235)—each ends with its own specific lead isotope (lead-208, lead-206, and lead-207 respectively). All these isotopes are stable and are also present in nature as [[primordial nuclide]]s, so their excess amounts in comparison with lead-204 (which has only a primordial origin) are required for accurate [[uranium–lead dating]] of rocks. Correlating more than one results in [[lead-lead dating]], capable of every greater accuracy.
{{Clear}}

=== Thorium series ===
[[Image:Decay Chain Thorium.svg|thumb|300px|right]]
The 4n chain of thorium-232 is commonly called the "thorium series" or "thorium cascade". Beginning with naturally occurring thorium-232, this series includes the following elements:  [[actinium]], [[bismuth]], lead, [[polonium]], radium, radon and [[thallium]].  All are present, at least transiently, in any natural thorium-containing sample, whether metal, compound, or mineral. The series terminates with lead-208.

Plutonium-244 (which appears several steps above thorium-232 in this chain if one extends it to the transuranics) was present in the early Solar System,<ref name=Davis/> and is just long-lived enough that it should still survive in trace quantities today,<ref name="PU244">{{cite journal | last1 = Hoffman | first1 = D. C. | last2 = Lawrence | first2 = F. O. | last3 = Mewherter | first3 = J. L. | last4 = Rourke | first4 = F. M. | year = 1971| title = Detection of Plutonium-244 in Nature | journal = [[Nature (journal)|Nature]] | volume =  234| issue = 5325 | pages =  132–134| doi = 10.1038/234132a0 | bibcode = 1971Natur.234..132H | s2cid = 4283169 }}</ref> though it is uncertain if it has been detected.<ref name="PRC">{{cite journal|last=Lachner|first=J.|display-authors=etal|date=2012|title=Attempt to detect primordial <sup>244</sup>Pu on Earth|journal=Physical Review C|volume=85|issue=1 |pages=015801| doi=10.1103/PhysRevC.85.015801|bibcode=2012PhRvC..85a5801L}}</ref>

The total energy released from thorium-232 to lead-208, including the energy lost to neutrinos, is 42.6&nbsp;MeV.

{| class="wikitable" style="margin:auto; text-align:center;"
!rowspan=2|Nuclide
!colspan=2|Historic names
!rowspan=2|Decay mode
!rowspan=2|Half-life<br />(''a'' = years)
!rowspan=2|Energy released<br/>MeV
!rowspan=2|Decay<br/>product
|-
!Short!!Long
|-
| [[Californium-252|<sup>252</sup>Cf]]
| 
| 
| [[alpha decay|α]]
| 2.645 a
| 6.1181
| [[Curium-248|<sup>248</sup>Cm]]
|-
| <sup>248</sup>Cm
| 
| 
| α
| 3.4{{e|5}} a
| 5.162
| [[Plutonium-244|<sup>244</sup>Pu]]
|-
|<sup>244</sup>Pu
|
|
|α
|8{{e|7}} a
|4.589
|[[Uranium-240|<sup>240</sup>U]]
|-
| <sup>240</sup>U
| 
| 
| [[beta decay|β<sup>−</sup>]]
| 14.1 h
| 0.39
| [[Neptunium-240|<sup>240</sup>Np]]
|-
| <sup>240</sup>Np
| 
| 
| β<sup>−</sup>
| 1.032 h
| 2.2
| [[Plutonium-240|<sup>240</sup>Pu]]
|-
| <sup>240</sup>Pu
| 
| 
| α
| 6561 a
| 5.1683
| [[Uranium-236|<sup>236</sup>U]]
|-
| <sup>236</sup>U
| 
| Thoruranium<ref name=thoruranium>{{cite journal |last1=Trenn |first1=Thaddeus J. |date=1978 |title=Thoruranium (U-236) as the extinct natural parent of thorium: The premature falsification of an essentially correct theory |journal=Annals of Science |volume=35 |issue=6 |pages=581–97 |doi=10.1080/00033797800200441}}</ref>
| α
| 2.3{{e|7}} a
| 4.494
| [[Thorium-232|<sup>232</sup>Th]]
|-
| <sup>232</sup>Th
| Th
| Thorium
| α
| 1.405{{e|10}} a
| 4.081
| [[Radium-228|<sup>228</sup>Ra]]
|-
| <sup>228</sup>Ra
| MsTh<sub>1</sub>
| Mesothorium 1
| β<sup>−</sup>
| 5.75 a
| 0.046
| [[Actinium-228|<sup>228</sup>Ac]]
|-
| <sup>228</sup>Ac
| MsTh<sub>2</sub>
| Mesothorium 2
| β<sup>−</sup>
| 6.25 h
| 2.124
| [[Thorium-228|<sup>228</sup>Th]]
|-
| <sup>228</sup>Th
| RdTh
| Radiothorium
| α
| 1.9116 a
| 5.520
| [[Radium-224|<sup>224</sup>Ra]]
|-
| <sup>224</sup>Ra
| ThX
| Thorium X
| α
| 3.6319 d
| 5.789
| [[Radon-220|<sup>220</sup>Rn]]
|-
| <sup>220</sup>Rn
| Tn
| Thoron,<br />Thorium Emanation
| α
| 55.6 s
| 6.404
| [[Polonium-216|<sup>216</sup>Po]]
|-
| <sup>216</sup>Po
| ThA
| Thorium A
| α
| 0.145 s
| 6.906
| [[Lead-212|<sup>212</sup>Pb]]
|-
| <sup>212</sup>Pb
| ThB
| Thorium B
| β<sup>−</sup>
| 10.64 h
| 0.570
| [[Bismuth-212|<sup>212</sup>Bi]]
|-
| <sup>212</sup>Bi
| ThC
| Thorium C
| β<sup>−</sup> 64.06% <br /> α 35.94%
| 60.55 min
| 2.252 <br /> 6.208
| [[Polonium-212|<sup>212</sup>Po]] <br /> [[Thallium-208|<sup>208</sup>Tl]]
|-
| <sup>212</sup>Po
| ThC′
| Thorium C′
| α
| 294.4 ns<ref>{{NUBASE2020}}</ref>
| 8.954<ref>{{cite web |author=[[National Nuclear Data Center]] |title=NuDat 3.0 database |url=https://www.nndc.bnl.gov/nudat3/ |publisher=[[Brookhaven National Laboratory]]|access-date=19 Feb 2022}}</ref>
| [[Lead-208|<sup>208</sup>Pb]]
|-
| <sup>208</sup>Tl
| ThC″
| Thorium C″
| β<sup>−</sup>
| 3.053 min
| 5.001<ref>{{Cite web|url=https://pripyat.mit.edu/KAERI/cgi-bin/nuclide?nuc=Tl-208|access-date=2025-04-04}}</ref>
| <sup>208</sup>Pb   
|-
| <sup>208</sup>Pb
| ThD
| Thorium D
| stable
| —
| —
| —
|}

===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
| .
| .
|}

=== {{anchor|Radium series}} Uranium series ===
[[Image:Decay chain(4n+2, Uranium series).svg|thumb|right|350px|alt=Uranium series|[[commons:File:Uranium series.gif|(More comprehensive graphic)]]]]
The 4n+2 chain of uranium-238 is called the "uranium series" or "radium series". Beginning with naturally occurring uranium-238, this series includes the following elements:  astatine, bismuth, [[lead]], [[mercury (element)|mercury]], polonium, [[protactinium]], [[radium]], [[radon]], thallium, and thorium.  All are present, at least transiently, in any natural uranium-containing sample, whether metal, compound, or mineral. The series terminates with lead-206.

The total energy released from uranium-238 to lead-206, including the energy lost to neutrinos, is 51.7&nbsp;MeV.

<!--{{Radium series/table}}-->
{| class="wikitable" style="margin:auto; text-align:center;"
!rowspan=2|Parent<br/>nuclide
!colspan=2|Historic name<ref name=th1>{{Thoennessen2016|pages=19}}</ref>
!rowspan=2|Decay mode <ref name="NdsEnsdf" group="RS">{{cite web|url=https://www-nds.iaea.org/relnsd/NdsEnsdf/QueryForm.html|title=Evaluated Nuclear Structure Data File|publisher=National Nuclear Data Center}}</ref>
!rowspan=2|Half-life<br />(''a''= years)
!rowspan=2 data-sort-type="number"|Energy released<br/>MeV<ref name="NdsEnsdf" group="RS"/>
!rowspan=2 data-sort-type="number"|Decay<br/>product<ref name="NdsEnsdf" group="RS"/>
|-
!Short!!Long
|-
| align="center"| [[Californium-250|<sup>250</sup>Cf]]
| align="center"| 
| align="center"| 
| align="center"| [[alpha decay|α]]
| align="center"| 13.08 a
| align="center"| 6.12844
| align="center"| [[Curium-246|<sup>246</sup>Cm]]
|-
| align="center"| [[Curium-246|<sup>246</sup>Cm]]
| align="center"| 
| align="center"| 
| align="center"| [[alpha decay|α]]
| align="center"| 4800 a
| align="center"| 5.47513
| align="center"| [[Plutonium-242|<sup>242</sup>Pu]]
|-
| align="center"| [[Plutonium-242|<sup>242</sup>Pu]]
| align="center"| 
| align="center"| 
| align="center"| [[alpha decay|α]]
| align="center"| 3.8×10<sup>5</sup> a
| align="center"| 4.98453
| align="center"| [[Uranium-238|<sup>238</sup>U]]
|-
| align="center"| [[Uranium-238|<sup>238</sup>U]]
| align="center"| U<sub>I</sub>
| align="center"| Uranium I
| align="center"| [[alpha decay|α]]
| align="center"| 4.468×10<sup>9</sup> a
| align="center"| 4.26975
| align="center"| [[Thorium-234|<sup>234</sup>Th]]
|-
| align="center"| [[Thorium-234|<sup>234</sup>Th]]
| align="center"| UX<sub>1</sub>
| align="center"| Uranium X<sub>1</sub>
| align="center"| [[beta decay|β<sup>−</sup>]]
| align="center"| 24.10 d
| align="center"| 0.273088
| align="center"| [[Protactinium-234|<sup>234m</sup>Pa]]
|-
| align="center"| [[Protactinium-234|<sup>234m</sup>Pa]]
| align="center"| UX<sub>2</sub>, Bv
| align="center"| Uranium X<sub>2</sub><br/>Brevium
| align="center"| [[Isomeric transition|IT]], 0.16%<br />[[beta decay|β<sup>−</sup>]], 99.84%
| align="center"| 1.159 min
| align="center"| 0.07392<br />2.268205
| align="center"| [[Protactinium-234|<sup>234</sup>Pa]]<br />[[Uranium-234|<sup>234</sup>U]]
|-
| align="center"| [[Protactinium-234|<sup>234</sup>Pa]]
| align="center"| UZ
| align="center"| Uranium Z
| align="center"| [[beta decay|β<sup>−</sup>]]
| align="center"| 6.70 h
| align="center"| 2.194285
| align="center"| [[Uranium-234|<sup>234</sup>U]]
|-
| align="center"| [[Uranium-234|<sup>234</sup>U]]
| align="center"| U<sub>II</sub>
| align="center"| Uranium II
| align="center"| [[alpha decay|α]]
| align="center"| 2.45×10<sup>5</sup> a
| align="center"| 4.8698
| align="center"| [[Thorium-230|<sup>230</sup>Th]]
|-
| align="center"| [[Thorium-230|<sup>230</sup>Th]]
| align="center"| Io
| align="center"| Ionium
| align="center"| [[alpha decay|α]]
| align="center"| 7.54×10<sup>4</sup> a
| align="center"| 4.76975
| align="center"| [[Radium-226|<sup>226</sup>Ra]]
|-
| align="center"| [[Radium-226|<sup>226</sup>Ra]]
| align="center"| Ra
| align="center"| Radium
| align="center"| [[alpha decay|α]]
| align="center"| 1600 a
| align="center"| 4.87062
| align="center"| [[radon-222|<sup>222</sup>Rn]]
|-
| align="center"| [[radon-222|<sup>222</sup>Rn]]
| align="center"| Rn
| align="center"| Radon,<br/>Radium Emanation
| align="center"| [[alpha decay|α]]
| align="center"| 3.8235 d
| align="center"| 5.59031
| align="center"| [[Polonium-218|<sup>218</sup>Po]]
|-
| align="center"| [[Polonium-218|<sup>218</sup>Po]]
| align="center"| RaA
| align="center"| Radium A
| align="center"| [[alpha decay|α]], 99.980%<br />[[beta decay|β<sup>−</sup>]], 0.020%
| align="center"| 3.098 min
| align="center"| 6.11468<br />0.259913
| align="center"| [[Lead-214|<sup>214</sup>Pb]]<br />[[Astatine-218|<sup>218</sup>At]]
|-
| align="center"| [[Astatine-218|<sup>218</sup>At]]
| align="center"| 
| align="center"| 
| align="center"| [[alpha decay|α]], 100%<br />[[beta decay|β<sup>−</sup>]]
| align="center"| 1.28 s
| align="center"| 6.874<br />2.881314
| align="center"| [[Bismuth-214|<sup>214</sup>Bi]]<br />[[Radon-218|<sup>218</sup>Rn]]
|-
| align="center"| [[Radon-218|<sup>218</sup>Rn]]
| align="center"| 
| align="center"| 
| align="center"| [[alpha decay|α]]
| align="center"| 35 ms
| align="center"| 7.26254
| align="center"| [[Polonium-214|<sup>214</sup>Po]]
|-
| align="center"| [[Lead-214|<sup>214</sup>Pb]]
| align="center"| RaB
| align="center"| Radium B
| align="center"| [[beta decay|β<sup>−</sup>]]
| align="center"| 26.8 min
| align="center"| 1.019237
| align="center"| [[Bismuth-214|<sup>214</sup>Bi]]
|-
| align="center"| [[Bismuth-214|<sup>214</sup>Bi]]
| align="center"| RaC	
| align="center"| Radium C
| align="center"| [[beta decay|β<sup>−</sup>]], 99.979%<br />[[alpha decay|α]], 0.021%
| align="center"| 19.9 min
| align="center"| 3.269857<br />5.62119
| align="center"| [[Polonium-214|<sup>214</sup>Po]]<br />[[Thallium-210|<sup>210</sup>Tl]]
|-
| align="center"| [[Polonium-214|<sup>214</sup>Po]]
| align="center"| RaC'
| align="center"| Radium C'
| align="center"| [[alpha decay|α]]
| align="center"| 164.3 μs
| align="center"| 7.83346
| align="center"| [[Lead-210|<sup>210</sup>Pb]]
|-
| align="center"| [[Thallium-210|<sup>210</sup>Tl]]
| align="center"| RaC"
| align="center"| Radium C"
| align="center"| [[beta decay|β<sup>−</sup>]]<br />[[Beta-delayed neutron emission|β<sup>−</sup>n]], 0.009%
| align="center"| 1.3 min
| align="center"| 5.48213<br />0.296
| align="center"| [[Lead-210|<sup>210</sup>Pb]]<br />[[Lead-209|<sup>209</sup>Pb]] (from neptunium series)
|-
| align="center"| [[Lead-210|<sup>210</sup>Pb]]
| align="center"| RaD
| align="center"| Radium D
| align="center"| [[beta decay|β<sup>−</sup>]], 100%<br />[[alpha decay|α]], 1.9×10<sup>−6</sup>%
| align="center"| 22.20 a
| align="center"| 0.063487<br />3.7923
| align="center"| [[Bismuth-210|<sup>210</sup>Bi]]<br />[[Mercury-206|<sup>206</sup>Hg]]
|-
| align="center"| [[Bismuth-210|<sup>210</sup>Bi]]
| align="center"| RaE
| align="center"| Radium E	
| align="center"| [[beta decay|β<sup>−</sup>]], 100%<br />[[alpha decay|α]], 1.32×10<sup>−4</sup>%
| align="center"| 5.012 d
| align="center"| 1.161234<br />5.03647
| align="center"| [[Polonium-210|<sup>210</sup>Po]]<br />[[Thallium-206|<sup>206</sup>Tl]]
|-
| align="center"| [[Polonium-210|<sup>210</sup>Po]]
| align="center"| RaF
| align="center"| Radium F
| align="center"| [[alpha decay|α]]
| align="center"| 138.376 d
| align="center"| 5.03647
| align="center"| [[Lead-206|<sup>206</sup>Pb]]
|-
| align="center"| [[Mercury-206|<sup>206</sup>Hg]]
| align="center"| 
| align="center"| 
| align="center"| [[beta decay|β<sup>−</sup>]]
| align="center"| 8.32 min
| align="center"| 1.307649
| align="center"| [[Thallium-206|<sup>206</sup>Tl]]
|-
| align="center"| [[Thallium-206|<sup>206</sup>Tl]]
| align="center"| RaE"
| align="center"| Radium E"
| align="center"| [[beta decay|β<sup>−</sup>]]
| align="center"| 4.202 min
| align="center"| 1.5322211
| align="center"| [[Lead-206|<sup>206</sup>Pb]]
|-
| align="center"| [[Lead-206|<sup>206</sup>Pb]]
| align="center"| RaG<ref>{{Cite journal|last=Kuhn|first=W.|date=1929|title=LXVIII. Scattering of thorium C" γ-radiation by radium G and ordinary lead|url=https://doi.org/10.1080/14786441108564923|journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science|volume=8|issue=52|pages=628|doi=10.1080/14786441108564923|issn=1941-5982|url-access=subscription}}</ref>
| align="center"| Radium G
| align="center"| stable
| align="center"| -
| align="center"| -
| align="center"| -
|}
{{reflist|group="RS"}}

=== Actinium series ===
The 4n+3 chain of [[uranium-235]] is commonly called the "actinium series" or "actinium cascade". Beginning with the naturally-occurring isotope uranium-235, this decay series includes the following elements:  actinium, [[astatine]], [[bismuth]], [[francium]], [[lead]], [[polonium]], [[protactinium]], radium, radon, [[thallium]], and [[thorium]]. All are present, at least transiently, in any sample containing uranium-235, whether metal, compound, ore, or mineral. This series terminates with the stable isotope [[lead-207]].
[[Image:Decay Chain of Actinium.svg|thumb|right|300px|alt=Actinium series|([[commons:File:Decay scheme U235.png|More detailed graphic]])]]

In the early Solar System this chain went back to <sup>247</sup>Cm. This manifests itself today as variations in <sup>235</sup>U/<sup>238</sup>U ratios, since [[curium]] and uranium have noticeably different chemistries and would have separated differently.<ref name=Davis/><ref>{{cite journal |last1=Tsaletka |first1=R. |last2=Lapitskii |first2=A. V. |date=1960 |title=Occurrence of the Transuranium Elements in Nature |url=https://www.russchemrev.org/RCR1264pdf |journal=Russian Chemical Reviews |volume=29 |issue=12 |pages=684–689 |doi= 10.1070/RC1960v029n12ABEH001264|bibcode=1960RuCRv..29..684T |access-date=20 January 2024}}</ref>

The total energy released from uranium-235 to lead-207, including the energy lost to neutrinos, is 46.4&nbsp;MeV.

{| class="wikitable" style="margin:auto; text-align:center;"
!rowspan=2|Nuclide
!colspan=2|Historic name
!rowspan=2|Decay mode
!rowspan=2|Half-life<br />(''a'' = years)
!rowspan=2|Energy released<br/>MeV
!rowspan=2|Decay<br/>product
|-
!Short!!Long
|-
| [[Californium-251|<sup>251</sup>Cf]]
| 
| 
| [[alpha decay|α]]
| 900.6&nbsp;a
| 6.176
| <sup>247</sup>Cm
|-
|[[Curium-247|<sup>247</sup>Cm]]
|
|
|α
|1.56×10<sup>7</sup> a
|5.353
|<sup>243</sup>Pu
|-
|[[Plutonium-243|<sup>243</sup>Pu]]
|
| 
| [[beta decay|β<sup>&minus;</sup>]]
| 4.95556&nbsp;h
| 0.579
| <sup>243</sup>Am
|-
| [[Americium-243|<sup>243</sup>Am]]
| 
| 
| α
| 7388&nbsp;a
| 5.439
| <sup>239</sup>Np
|-
| [[Neptunium-239|<sup>239</sup>Np]]
| 
| 
| β<sup>&minus;</sup>
| 2.3565&nbsp;d
| 0.723
| <sup>239</sup>Pu
|-
| [[Plutonium-239|<sup>239</sup>Pu]]
| 
| 
| α
| align="center"| 2.41×10<sup>4</sup> a
| align="center"| 5.244
| align="center"| <sup>235</sup>U
|-
| align="center"| <sup>235</sup>U
| align="center"| AcU
| align="center"| Actino-uranium
| align="center"|  α
| align="center"| 7.04×10<sup>8</sup> a
| align="center"| 4.678
| align="center"| [[Thorium-231|<sup>231</sup>Th]]
|-
| align="center"| <sup>231</sup>Th
| align="center"| UY
| align="center"| Uranium Y
| align="center"| β<sup>−</sup>
| align="center"| 25.52 h
| align="center"| 0.391
| align="center"| [[Protactinium-231|<sup>231</sup>Pa]]
|-
| align="center"| <sup>231</sup>Pa
| align="center"| Pa
| align="center"| Protoactinium
| align="center"| α
| align="center"| 32760 a
| align="center"| 5.150
| align="center"| [[Actinium-227|<sup>227</sup>Ac]]
|-
| align="center"| <sup>227</sup>Ac
| align="center"| Ac
| align="center"| Actinium
| align="center"| β<sup>−</sup> 98.62% <br /> α 1.38%
| align="center"| 21.772 a
| align="center"| 0.045 <br /> 5.042
| align="center"| [[Thorium-227|<sup>227</sup>Th]] <br /> [[Francium-223|<sup>223</sup>Fr]]
|-
| align="center"| <sup>227</sup>Th
| align="center"| RdAc
| align="center"| Radioactinium
| align="center"|  α
| align="center"| 18.68 d
| align="center"| 6.147
| align="center"| [[Radium-223|<sup>223</sup>Ra]]
|-
| align="center"| <sup>223</sup>Fr
| align="center"| AcK
| align="center"| Actinium K
| align="center"|  β<sup>−</sup> 99.994% <br /> α 0.006%
| align="center"| 22.00 min
| align="center"| 1.149 <br /> 5.340
| align="center"| <sup>223</sup>Ra <br /> [[Astatine-219|<sup>219</sup>At]]
|-
| align="center"| <sup>223</sup>Ra
| align="center"| AcX
| align="center"| Actinium X
| align="center"|  α
| align="center"| 11.43 d
| align="center"| 5.979
| align="center"| [[Radon-219|<sup>219</sup>Rn]]
|-
| align="center"| <sup>219</sup>At
| align="center"|
| align="center"|
| align="center"|  α 97.00% <br /> β<sup>−</sup> 3.00%
| align="center"| 56 s
| align="center"| 6.275 <br /> 1.700
| align="center"| [[Bismuth-215|<sup>215</sup>Bi]] <br /> <sup>219</sup>Rn
|-
| align="center"| <sup>219</sup>Rn
| align="center"| An
| align="center"| Actinon,<br />Actinium Emanation
| align="center"|  α
| align="center"| 3.96 s
| align="center"| 6.946
| align="center"| [[Polonium-215|<sup>215</sup>Po]]
|-
| align="center"| <sup>215</sup>Bi
| align="center"|
| align="center"|
| align="center"|  β<sup>−</sup>
| align="center"| 7.6 min
| align="center"| 2.250  	
| align="center"| <sup>215</sup>Po
|-
| align="center"| <sup>215</sup>Po
| align="center"| AcA
| align="center"| Actinium A
| align="center"|  α 99.99977% <br />  β<sup>−</sup> 0.00023%
| align="center"| 1.781 ms
| align="center"| 7.527 <br /> 0.715
| align="center"| [[Lead-211|<sup>211</sup>Pb]] <br /> [[Astatine-215|<sup>215</sup>At]]
|-
| align="center"| <sup>215</sup>At
| align="center"|
| align="center"|
| align="center"|  α
| align="center"| 0.1 ms
| align="center"| 8.178
| align="center"| [[Bismuth-211|<sup>211</sup>Bi]]
|-
| align="center"| <sup>211</sup>Pb
| align="center"| AcB
| align="center"| Actinium B
| align="center"|  β<sup>−</sup>
| align="center"| 36.1 min
| align="center"| 1.367
| align="center"| <sup>211</sup>Bi
|-
| align="center"| <sup>211</sup>Bi
| align="center"| AcC
| align="center"| Actinium C
| align="center"|  α 99.724% <br />  β<sup>−</sup> 0.276%
| align="center"| 2.14 min
| align="center"| 6.751 <br /> 0.575
| align="center"| [[Thallium-207|<sup>207</sup>Tl]] <br /> [[Polonium-211|<sup>211</sup>Po]]
|-
| align="center"| <sup>211</sup>Po
| align="center"| AcC'
| align="center"| Actinium C'
| align="center"|  α
| align="center"| 516 ms
| align="center"| 7.595
| align="center"| [[Lead-207|<sup>207</sup>Pb]]
|-
| align="center"| <sup>207</sup>Tl
| align="center"| AcC"
| align="center"| Actinium C"
| align="center"| β<sup>−</sup>
| align="center"| 4.77 min
| align="center"| 1.418
| align="center"| <sup>207</sup>Pb
|-
| align="center"| <sup>207</sup>Pb
| align="center"| AcD
| align="center"| Actinium D
| align="center"| .
| align="center"| stable
| align="center"| .
| align="center"| .
|}

== See also ==
* [[Nuclear physics]]
* [[Radioactive decay]]
* [[Valley of stability]]
* [[Decay product]]
* [[Radioisotopes]] ([[radionuclide]])
* [[Radiometric dating]]

== Notes ==
{{reflist}}

== References ==
*{{cite book
 |author1=C.M. Lederer |author2=J.M. Hollander |author3=I. Perlman |year=1968
 |title=Table of Isotopes
 |edition=6th
 |location=New York
 |publisher=[[John Wiley & Sons]]
}}

== External links ==
{{commons category|Decay chain}}
* [http://www.nucleonica.com Nucleonica nuclear science portal]
* [http://www.nucleonica.com/wiki/index.php?title=Help%3ADecay_Engine Nucleonica's Decay Engine for professional online decay calculations]
* [https://www.epa.gov/radiation/radioactive-decay EPA – Radioactive Decay]
* [https://web.archive.org/web/20061205022425/http://ie.lbl.gov/education/isotopes.htm Government website listing isotopes and decay energies]
* [http://www.nndc.bnl.gov National Nuclear Data Center] – freely available databases that can be used to check or construct decay chains
* [[Image:Ndslivechart.png]] [http://www-nds.iaea.org/livechart IAEA – Live Chart of Nuclides] (with decay chains)
* [http://www.wolframalpha.com/widgets/gallery/view.jsp?id=23174474f31785ce939641039a212de4 Decay Chain Finder]

[[Category:Radioactivity]]