Decay chain
A decay chain, also called a radioactive series, is a sequence of nuclides in which each nuclide transforms into the next by radioactive decay until a stable nuclide is reached.[1] There are three "classical" decay chains, which describe the decay of the naturally-occuring actinoids; a fourth long decay chain has become extinct in natural sources, but is known from artificially-produced radionuclides.[2] Shorter decay chains describe the decay of the transfermium elements and lighter non-actinoid radionuclides.
The principle of a decay chain comes from the radioactive displacement law, deduced in 1913 by Fajans,[3][4] Soddy[5][6] and Russell.[7] The original version of the law, which describes the most common forms of radioactive decay, is that
- alpha decay leads to a nuclide with an atomic number two lower than the decaying nuclide, and a mass number four lower;
- beta decay[note 1] leads to a nuclide with the same mass number as the decaying nuclide but with an atomic number one higher.
The discovery (1914) of a difference in atomic weight between lead samples from thorium and uranium minerals,[8][9] as predicted by Fajans,[3] was conclusive proof of the corresponding decay chains.[10][11]
Actinoid decay chains
Because alpha decay changes the mass number by four, while beta decay does not change the mass number at all, all the nuclides in a decay chain have the same value of mod 4(A), and the chains can be distinguished as those where A = 4n, or 4n+1, etc. for all the nuclides in the chain.
Thorium (4n) series
Neptunium (4n+1) series
Uranium (4n+2) series
Actinium (4n+3) series
| Uranium-235 (α, 7.04 × 108 a) | |||
| Thorium-231 (β−, 25.52 h) | |||
| Protactinium-231 (α, 3.276 × 104 a) | |||
| Actinium-227 (21.772 a) | |||
| β−, 98.62% | α, 1.38% | ||
| Thorium-227 (α, 18.68 d) |
Francium-223 (22.00 min) | ||
| β−, 99.994% | α, 0.006% | ||
| Radium-223 (α, 11.43 d) |
Astatine-219 (56 s) | ||
| β−, 3.00% | α, 97.00% | ||
| Radon-219 (α, 3.96 s) |
Bismuth-215 (β−, 7.6 min) | ||
| Polonium-215 (1.781 ms) | |||
| α, 99.99977% | β−, 0.00033% | ||
| Lead-211 (β−, 36.1 min) |
Astatine-215 (α, 0.1 ms) | ||
| Bismuth-211 (2.14 min) | |||
| α, 99.724% | β−, 0.276% | ||
| Thallium-207 (β−, 4.77 min) |
Polonium-211 (α, 516 ms) | ||
| Lead-207 (STABLE) | |||
Notes and references
Notes
- ↑ This description applies to β− decay, which was the only type of beta decay known in 1913.
References
- ↑ decay chain, <http://goldbook.iupac.org/D01537.html> (accessed 18 April 2011), Compendium of Chemical Terminology Internet edition; International Union of Pure and Applied Chemistry (IUPAC).
- ↑ Seaborg, Glenn T. The Neptunium (4n + 1) Radioactive Family. Chem. Eng. News 1948, 26 (26), 1902–6. DOI: 10.1021/cen-v026n026.p1902.
- ↑ 3.0 3.1 Fajans, Kasimir Die radioaktiven Umwandlungen und das periodische System der Elemente. Ber. Dtsch. Chem. Ges. 1913, 46, 422–39. DOI: 10.1002/cber.19130460162. Translated excerpt
- ↑ Fajans, K. Phys. Z. 1913, 14, 131–36. Fajans, K. Phys. Z. 1913, 14, 136–42. Fajans, K. Radium 1913, 10, 61.
- ↑ Soddy, Frederick The Radio-elements and the Periodic Law. Chem. News 1913, 107, 97–99, <http://web.lemoyne.edu/~giunta/soddycn.html>.
- ↑ Soddy, Frederick Radioactivity. Annu. Rep. Prog. Chem. 1913, 10, 262–88. DOI: 10.1039/AR9131000262.
- ↑ Russell, Alexander S. The periodic system and the radio-elements. Chem. News 1913, 107, 49–52.
- ↑ Soddy, Frederick; Hyman, Henry The atomic weight of lead from ceylon thorite. J. Chem. Soc., Trans. 1914, 105, 1402–8. DOI: 10.1039/CT9140501402.
- ↑ Richards, Theodore W.; Lembert, Max E. The Atomic Weight of Lead of Radioactive Origin. J. Am. Chem. Soc. 1914, 36 (7), 1329–44. DOI: 10.1021/ja02184a001.
- ↑ Anders, Oswald U. The place of isotopes in the periodic table: The 50th anniversary of the Fajans–Soddy displacement laws. J. Chem. Educ. 1964, 41 (10), 522. DOI: 10.1021/ed041p522.
- ↑ Kauffman, George B. The atomic weight of lead of radioactive origin: A confirmation of the concept of isotopy and the group displacement laws. Part I. J. Chem. Educ. 1982, 59 (1), 3. DOI: 10.1021/ed059p3. Kauffman, George B. The atomic weight of lead of radioactive origin: A confirmation of the concept of isotopy and the group displacement laws. Part II. J. Chem. Educ. 1982, 59 (2), 119. DOI: 10.1021/ed059p119.
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