Decay chain

A decay chain is generally the sequence of the products of the radioactive decay that occurs when a radioactive nuclide is converted into other nuclides ( " breaks down "). The first resulting nuclide is called the daughter nuclide, the daughter nuclide has the following Enkelnuklid that the Enkelnuklid following Urenkelnuklid etc.

Particularly important are the decay chains of heavy natural radionuclides such as uranium and thorium. The natural decay modes can be either the mass number unchanged, as the epsilon - and beta decay ( a neutron is converted into a proton ), or decrease it to four units ( alpha decay ). This results in heavy natural radionuclides four different decay series. The mass number (written on the left superscript on the formula symbol of the nuclide ), it ranks above the rest when divided by four of these decay chains unambiguously.

The natural decay chains

There are three completely existing natural decay series:

  • Uranium - radium series: nuclide uranium -238, Endnuklid lead- 206; (4n 2 series )
  • Uranium - actinium series: nuclide uranium -235, with the extension to the artificial transuranic elements plutonium -239 is the first precursor stage of uranium -235, Endnuklid lead- 207; (4n 3 series )
  • Thorium series: nuclide thorium -232, but are still available until his Vorgängernuklide plutonium -244 on the earth, so that, strictly speaking, the series begins there. Endnuklid lead-208; (4n series)

The fourth decay chain comes to the last step in nature (no longer), because the long-lived, is almost completely disintegrated eponymous stage and early- neptunium -237 in this series and most intermediates have short half-lives. Only the last radionuclide in this series, bismuth -209 is, because of its extremely long half-life still exists and was therefore kept even long for the Endnuklid the series, was discovered by 2003 that it is an alpha emitter with 19 trillion years half-life.

  • Neptunium series: nuclide is the name neptunium- 237th Often, however, plutonium -241 is considered to be their parent nuclide, Endnuklid thallium - 205; (4n 1 series )

From an existing amount of an unstable nuclide is formed by a mixture of nuclides decay that follow him in the decay chain, before eventually have the series through to the Endnuklid all cores. In the mixture nuclides with short half-life are present only in small quantities, while those accumulate with longer half -life correspondingly stronger.

Position in the chart of nuclides

Historic designations

In the classical period of research into the radioactive decay series the various nuclides were referred to by other names, to which the membership revealed a natural decay series and the similarity in the properties (eg, are radon, thoron and Actinon all noble gases ):

The three natural decay chains saw in this old notation as follows:

  • Thorium series: Th → → MsTh1 MsTh2 → → RdTh ThX → Tn → ThA → ThB → → ThC ThC '(or ThC ") → ThD
  • Uranium - radium series: UI → → UX1 UX2 (→ UZ) → → UII Io → Ra → Rn → Ra → Ra → → RaC RaC '(or RaC ' ) → → RaD RaE → → RaF RaG
  • Uranium - actinium series: AcU → UY → Pa → Ac → RDAC (or ACK) → → On → AcA AcX AcB → → → AcC AcC "(or AcC ') → AcD
Decay chain#Radium series .28also known as uranium series.29 Decay chain#Actinium series Decay chain#Thorium series Decay chain#Neptunium series Neutron number Curium Americium Francium Astatine Polonium Digital Object Identifier
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