| Nuclear physics |
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High-energy processes |
Innuclear science adecay chain refers to the predictable series ofradioactive disintegrations undergone by the nuclei of certain unstable chemical elements.
Radioactive isotopes do not usually decay directly tostable 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 astable isotope, whose nucleus no longer has the surplus of energy necessary to produce another emission of radiation. Such stable isotopes are then said to have nuclei that have reached theirground states.
The stages or steps in a decay chain are referred to by their relationship to previous or subsequent stages. Hence, aparent isotope is one that undergoes decay to form adaughter isotope. For example element 92,uranium, has an isotope with 144 neutrons (236U) and it decays into an isotope of element 90,thorium, with 142 neutrons (232Th). The daughter isotope may be stable or it may itself decay to form another daughter isotope.232Th does this when it decays intoradium-228. The daughter of a daughter isotope, such as228Ra, is sometimes called agranddaughter 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 isnot known to have determinable causes and the time at which it occurs is thereforecompletely 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 decayingexponential distribution with adecay constant (λ) particular to the isotope. On this understanding the radioactive decay of an initial population of unstable atoms over timet follows the curve given bye−λt.
One of the most important properties of any radioactive material follows from this analysis, itshalf-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 canrange from nearly instantaneous—hydrogen-5 decays in lesstime than it takes for a photon to go from one end of its nucleus to the other—to fourteenorders of magnitude longer than theage of the universe:tellurium-128 has a half-life of2.2×1024 years.
TheBateman 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 inequilibrium. A sample of radioactive material inequilibrium 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 beout of equilibrium. An unintuitive consequence of this disequilibrium is that a sample ofenriched material may occasionally increase in radioactivity as daughter products that are more highly radioactive than their parents accumulate. Bothenriched anddepleted uranium provide examples of this phenomenon.
The chemical elements came into being in two phases. The first commenced shortly after theBig Bang. From ten seconds to 20 minutes after the beginning of the universe theearliest 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 ofhydrogen—protium,deuterium andtritium—and two of the nine known isotopes ofhelium—helium-3 andhelium-4. Trace amounts oflithium-7 andberyllium-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 ofnucleosynthesis that commenced with the birth of thefirst stars.[1] The nuclear furnaces that power stellar evolution were necessary to create large quantities of all elements heavier than helium, and ther- ands-processes of neutron capture that occur in stellar cores are thought to have created all such elements up toiron andnickel (atomic numbers 26 and 28). Theextreme conditions that attendsupernovae explosions are capable of creating the elements betweenoxygen andrubidium (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 duringneutron 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 ofour planet's condensation from the solarprotoplanetary disc, around 4.5 billion years ago. The exceptions to these so-calledprimordial 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 onatomic weapons, nuclear reactors (natural ormanmade) or the laborious atom-by-atomassembly of nuclei withparticle 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 ashelium-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 inuranium-238). No nuclide heavier than lead-208 is stable; these heavier elements have to shed mass to achieve stability, mostly byalpha decay. The other common way for isotopes with a high neutron to proton ratio (n/p) to decay isbeta 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 aninverse 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 orelectron 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] This is because there are just two main decay methods:alpha radiation, which reduces the mass by 4atomic 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 + 1, 4n + 2, and 4n + 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 ofnihonium-278 synthesised underwent six alpha decays down tomendelevium-254,[2] followed by anelectron capture (a form of beta decay) tofermium-254,[2] and then a seventh alpha tocalifornium-250,[2] upon which it would have followed the 4n + 2 chain (radium series) as given in this article. However, the heaviestsuperheavy nuclides synthesised do not reach the four decay chains, because they reach aspontaneously fissioning nuclide after a few alpha decays that terminates the chain: this is what happened to the first two atoms of nihonium-278 synthesised,[3][4] 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;[5] 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,244Pu,237Np, and247Cm 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.[6] (There is no nuclide with a half-life over a million years above238U 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.[7] The tables below hence start the four decay chains at isotopes ofcalifornium with mass numbers from 249 to 252.
| Name of series | Thorium | Neptunium | Uranium | Actinium |
| Mass numbers | 4n | 4n+1 | 4n+2 | 4n+3 |
| Long-lived nuclide | 232Th (244Pu) | 209Bi (237Np) | 238U | 235U (247Cm) |
| Half-life (billions of years) | 14 (0.08) | 20100000000 (0.00214) | 4.5 | 0.7 (0.0156) |
| End of chain | 208Pb | 205Tl | 206Pb | 207Pb |
These four chains are summarised in the chart in the following section.
The four most common modes of radioactive decay are: alpha decay, beta decay,inverse beta decay (considered as both positron emission and electron capture), andisomeric transition. Of these decay processes, only alpha decay (fission of ahelium-4 nucleus) changes theatomic 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 sameresidue 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 theactinium series, representing three of these four classes, and ending in three different, stable isotopes oflead. The mass number of every isotope in these chains can be represented asA = 4n,A = 4n + 2, and A = 4n + 3, respectively. The long-lived starting isotopes of these three isotopes, respectivelythorium-232,uranium-238, anduranium-235, have existed since the formation of the Earth, ignoring the artificial isotopes and their decays created since the 1940s.
Due to the relatively shorthalf-life of its starting isotopeneptunium-237 (2.14 million years), the fourth chain, theneptunium series withA = 4n + 1, is already extinct in nature, except for the final rate-limiting step, decay ofbismuth-209. Traces of237Np and its decay products do occur in nature, however, as a result of neutron capture in uranium ore.[8] The ending isotope of this chain is now known to bethallium-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 of2.01×1019 years.[9]
There are also non-transuranic decay chains of unstable isotopes of light elements, for example those ofmagnesium-28 andchlorine-39. On Earth, most of the starting isotopes of these chains before 1945 were generated bycosmic radiation. Since 1945, the testing and use of nuclear weapons has also released numerous radioactivefission products. Almost all such isotopes decay by either β− or β+ 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 decay into stability.
| Actinides[10] bydecay chain | Half-life range (a) | Fission products of235U byyield[11] | ||||||
|---|---|---|---|---|---|---|---|---|
| 4n | 4n + 1 | 4n + 2 | 4n + 3 | 4.5–7% | 0.04–1.25% | <0.001% | ||
| 228Ra№ | 4–6 a | 155Euþ | ||||||
| 248Bk[12] | > 9 a | |||||||
| 244Cmƒ | 241Puƒ | 250Cf | 227Ac№ | 10–29 a | 90Sr | 85Kr | 113mCdþ | |
| 232Uƒ | 238Puƒ | 243Cmƒ | 29–97 a | 137Cs | 151Smþ | 121mSn | ||
| 249Cfƒ | 242mAmƒ | 141–351 a | No fission products have ahalf-life | |||||
| 241Amƒ | 251Cfƒ[13] | 430–900 a | ||||||
| 226Ra№ | 247Bk | 1.3–1.6 ka | ||||||
| 240Pu | 229Th | 246Cmƒ | 243Amƒ | 4.7–7.4 ka | ||||
| 245Cmƒ | 250Cm | 8.3–8.5 ka | ||||||
| 239Puƒ | 24.1 ka | |||||||
| 230Th№ | 231Pa№ | 32–76 ka | ||||||
| 236Npƒ | 233Uƒ | 234U№ | 150–250 ka | 99Tc₡ | 126Sn | |||
| 248Cm | 242Pu | 327–375 ka | 79Se₡ | |||||
| 1.33 Ma | 135Cs₡ | |||||||
| 237Npƒ | 1.61–6.5 Ma | 93Zr | 107Pd | |||||
| 236U | 247Cmƒ | 15–24 Ma | 129I₡ | |||||
| 244Pu | 80 Ma | ... nor beyond 15.7 Ma[14] | ||||||
| 232Th№ | 238U№ | 235Uƒ№ | 0.7–14.1 Ga | |||||
| ||||||||
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 (electrons,alpha particles,gamma quanta,neutrinos,Auger electrons andX-rays) and the recoil nucleus, assuming that the original nucleus was at rest. The letter 'a' represents a year (from the Latinannus).
In the tables below (except neptunium), the historic names of the naturally occurring nuclides are also given. These names were used at the time when the decay chains were first discovered and investigated. From these historical names one can locate the particular chain to which the nuclide belongs, and replace it with its modern name.
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 asprimordial nuclides, but their excess amounts in comparison with lead-204 (which has only a primordial origin) can be used in the technique ofuranium–lead dating to date rocks.
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 andthallium. 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,[6] and is just long-lived enough that it should still survive in trace quantities today,[15] though it is uncertain if it has been detected.[16]
The total energy released from thorium-232 to lead-208, including the energy lost to neutrinos, is 42.6 MeV.
| Nuclide | Historic names | Decay mode | Half-life (a = years) | Energy released MeV | Decay product | |
|---|---|---|---|---|---|---|
| Short | Long | |||||
| 252Cf | α | 2.645 a | 6.1181 | 248Cm | ||
| 248Cm | α | 3.4×105 a | 5.162 | 244Pu | ||
| 244Pu | α | 8×107 a | 4.589 | 240U | ||
| 240U | β− | 14.1 h | 0.39 | 240Np | ||
| 240Np | β− | 1.032 h | 2.2 | 240Pu | ||
| 240Pu | α | 6561 a | 5.1683 | 236U | ||
| 236U | Thoruranium[17] | α | 2.3×107 a | 4.494 | 232Th | |
| 232Th | Th | Thorium | α | 1.405×1010 a | 4.081 | 228Ra |
| 228Ra | MsTh1 | Mesothorium 1 | β− | 5.75 a | 0.046 | 228Ac |
| 228Ac | MsTh2 | Mesothorium 2 | β− | 6.25 h | 2.124 | 228Th |
| 228Th | RdTh | Radiothorium | α | 1.9116 a | 5.520 | 224Ra |
| 224Ra | ThX | Thorium X | α | 3.6319 d | 5.789 | 220Rn |
| 220Rn | Tn | Thoron, Thorium Emanation | α | 55.6 s | 6.404 | 216Po |
| 216Po | ThA | Thorium A | α | 0.145 s | 6.906 | 212Pb |
| 212Pb | ThB | Thorium B | β− | 10.64 h | 0.570 | 212Bi |
| 212Bi | ThC | Thorium C | β− 64.06% α 35.94% | 60.55 min | 2.252 6.208 | 212Po 208Tl |
| 212Po | ThC′ | Thorium C′ | α | 294.4 ns[18] | 8.954[19] | 208Pb |
| 208Tl | ThC″ | Thorium C″ | β− | 3.053 min | 5.001[20] | 208Pb |
| 208Pb | ThD | Thorium D | stable | — | — | — |
.svg)
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 of237Np produced by the (n,2n)knockout reaction in primordial238U.[8] Asmoke detector containing anamericium-241 ionization chamber accumulates a significant amount ofneptunium-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, anduranium. Since this series was only discovered and studied in 1947–1948,[21] its nuclides do not have 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 toneutrinos, is 66.8 MeV.
| Nuclide | Decay mode | Half-life (a = years) | Energy released MeV | Decay product |
|---|---|---|---|---|
| 249Cf | α | 351 a | 5.813+.388 | 245Cm |
| 245Cm | α | 8500 a | 5.362+.175 | 241Pu |
| 241Pu | β− | 14.4 a | 0.021 | 241Am |
| 241Am | α | 432.7 a | 5.638 | 237Np |
| 237Np | α | 2.14×106 a | 4.959 | 233Pa |
| 233Pa | β− | 27.0 d | 0.571 | 233U |
| 233U | α | 1.592×105 a | 4.909 | 229Th |
| 229Th | α | 7340 a | 5.168 | 225Ra |
| 225Ra | β− 99.998% α 0.002% | 14.9 d | 0.36 5.097 | 225Ac 221Rn |
| 225Ac | α | 10.0 d | 5.935 | 221Fr |
| 221Rn | β− 78% α 22% | 25.7 min | 1.194 6.163 | 221Fr 217Po |
| 221Fr | α 99.9952% β− 0.0048% | 4.8 min | 6.458 0.314 | 217At 221Ra |
| 221Ra | α | 28 s | 6.880 | 217Rn |
| 217Po | α 97.5% β− 2.5% | 1.53 s | 6.662 1.488 | 213Pb 217At |
| 217At | α 99.992% β− 0.008% | 32 ms | 7.201 0.737 | 213Bi 217Rn |
| 217Rn | α | 540 μs | 7.887 | 213Po |
| 213Pb | β− | 10.2 min | 2.028 | 213Bi |
| 213Bi | β− 97.80% α 2.20% | 46.5 min | 1.423 5.87 | 213Po 209Tl |
| 213Po | α | 3.72 μs | 8.536 | 209Pb |
| 209Tl | β− | 2.2 min | 3.99 | 209Pb |
| 209Pb | β− | 3.25 h | 0.644 | 209Bi |
| 209Bi | α | 2.01×1019 a | 3.137 | 205Tl |
| 205Tl | . | stable | . | . |
.svg)
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, 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 MeV.
| Parent nuclide | Historic name[22] | Decay mode[RS 1] | Half-life (a= years) | Energy released MeV[RS 1] | Decay product[RS 1] | |
|---|---|---|---|---|---|---|
| Short | Long | |||||
| 250Cf | α | 13.08 a | 6.12844 | 246Cm | ||
| 246Cm | α | 4800 a | 5.47513 | 242Pu | ||
| 242Pu | α | 3.8×105 a | 4.98453 | 238U | ||
| 238U | UI | Uranium I | α | 4.468×109 a | 4.26975 | 234Th |
| 234Th | UX1 | Uranium X1 | β− | 24.10 d | 0.273088 | 234mPa |
| 234mPa | UX2, Bv | Uranium X2 Brevium | IT, 0.16% β−, 99.84% | 1.159 min | 0.07392 2.268205 | 234Pa 234U |
| 234Pa | UZ | Uranium Z | β− | 6.70 h | 2.194285 | 234U |
| 234U | UII | Uranium II | α | 2.45×105 a | 4.8698 | 230Th |
| 230Th | Io | Ionium | α | 7.54×104 a | 4.76975 | 226Ra |
| 226Ra | Ra | Radium | α | 1600 a | 4.87062 | 222Rn |
| 222Rn | Rn | Radon, Radium Emanation | α | 3.8235 d | 5.59031 | 218Po |
| 218Po | RaA | Radium A | α, 99.980% β−, 0.020% | 3.098 min | 6.11468 0.259913 | 214Pb 218At |
| 218At | α, 99.9% β−, 0.1% | 1.5 s | 6.874 2.881314 | 214Bi 218Rn | ||
| 218Rn | α | 35 ms | 7.26254 | 214Po | ||
| 214Pb | RaB | Radium B | β− | 26.8 min | 1.019237 | 214Bi |
| 214Bi | RaC | Radium C | β−, 99.979% α, 0.021% | 19.9 min | 3.269857 5.62119 | 214Po 210Tl |
| 214Po | RaC' | Radium C' | α | 164.3 μs | 7.83346 | 210Pb |
| 210Tl | RaC" | Radium C" | β− β−n, 0.009% | 1.3 min | 5.48213 0.296 | 210Pb 209Pb (from neptunium series) |
| 210Pb | RaD | Radium D | β−, 100% α, 1.9×10−6% | 22.20 a | 0.063487 3.7923 | 210Bi 206Hg |
| 210Bi | RaE | Radium E | β−, 100% α, 1.32×10−4% | 5.012 d | 1.161234 5.03647 | 210Po 206Tl |
| 210Po | RaF | Radium F | α | 138.376 d | 5.03647 | 206Pb |
| 206Hg | β− | 8.32 min | 1.307649 | 206Tl | ||
| 206Tl | β− | 4.202 min | 1.5322211 | 206Pb | ||
| 206Pb | RaG[23] | Radium G | stable | - | - | - |
The 4n+3 chain ofuranium-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, andthorium. All are present, at least transiently, in any sample containing uranium-235, whether metal, compound, ore, or mineral. This series terminates with the stable isotopelead-207.
In the early Solar System this chain went back to247Cm. This manifests itself today as variations in235U/238U ratios, sincecurium and uranium have noticeably different chemistries and would have separated differently.[6][24]
The total energy released from uranium-235 to lead-207, including the energy lost to neutrinos, is 46.4 MeV.
| Nuclide | Historic name | Decay mode | Half-life (a = years) | Energy released MeV | Decay product | |
|---|---|---|---|---|---|---|
| Short | Long | |||||
| 251Cf | α | 900.6 a | 6.176 | 247Cm | ||
| 247Cm | α | 1.56×107 a | 5.353 | 243Pu | ||
| 243Pu | β− | 4.95556 h | 0.579 | 243Am | ||
| 243Am | α | 7388 a | 5.439 | 239Np | ||
| 239Np | β− | 2.3565 d | 0.723 | 239Pu | ||
| 239Pu | α | 2.41×104 a | 5.244 | 235U | ||
| 235U | AcU | Actin Uranium | α | 7.04×108 a | 4.678 | 231Th |
| 231Th | UY | Uranium Y | β− | 25.52 h | 0.391 | 231Pa |
| 231Pa | Pa | Protactinium | α | 32760 a | 5.150 | 227Ac |
| 227Ac | Ac | Actinium | β− 98.62% α 1.38% | 21.772 a | 0.045 5.042 | 227Th 223Fr |
| 227Th | RdAc | Radioactinium | α | 18.68 d | 6.147 | 223Ra |
| 223Fr | AcK | Actinium K | β− 99.994% α 0.006% | 22.00 min | 1.149 5.340 | 223Ra 219At |
| 223Ra | AcX | Actinium X | α | 11.43 d | 5.979 | 219Rn |
| 219At | α 97.00% β− 3.00% | 56 s | 6.275 1.700 | 215Bi 219Rn | ||
| 219Rn | An | Actinon, Actinium Emanation | α | 3.96 s | 6.946 | 215Po |
| 215Bi | β− | 7.6 min | 2.250 | 215Po | ||
| 215Po | AcA | Actinium A | α 99.99977% β− 0.00023% | 1.781 ms | 7.527 0.715 | 211Pb 215At |
| 215At | α | 0.1 ms | 8.178 | 211Bi | ||
| 211Pb | AcB | Actinium B | β− | 36.1 min | 1.367 | 211Bi |
| 211Bi | AcC | Actinium C | α 99.724% β− 0.276% | 2.14 min | 6.751 0.575 | 207Tl 211Po |
| 211Po | AcC' | Actinium C' | α | 516 ms | 7.595 | 207Pb |
| 207Tl | AcC" | Actinium C" | β− | 4.77 min | 1.418 | 207Pb |
| 207Pb | AcD | Actinium D | . | stable | . | . |
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IAEA – Live Chart of Nuclides (with decay chains)