The actinium series

URANIUM compounds), Pb from the thorium series, and Pb from the actinium series (see Actinides and transactinides). The crystal stmcture of lead is face-centered cubic the length of the edge of the cell is 0.49389 nm the number of atoms per unit cell is four. Other properties are Hsted in Table 1. 

Lefuma J, Chameaud J, Perraud R, et al. 1976. [An experimental study on a comparison between the toxic effects of radon-222 and its daughters on the lungs, and those exerted by alpha-emitters of the actinium series.] Occup Saf Health Ser 32 43-53. (French). 

ISOTOPES There are 41 isotopes of polonium. They range from Po-188 to Po-219. All of them are radioactive with half-lives ranging from a few milliseconds to 102 years, the latter for its most stable isotope Po-209. Polonium is involved with several radioactive decay series, including the actinium series, Po-211 and Po-215 the thorium series, Po-212 and Po-216 and the uranium decay series, Po-210, Po-214, and Po-218. 

The chemistry of neptunium (jjNp) is somewhat similar to that of uranium (gjU) and plutonium (g4Pu), which immediately precede and follow it in the actinide series on the periodic table. The discovery of neptunium provided a solution to a puzzle as to the missing decay products of the thorium decay series, in which all the elements have mass numbers evenly divisible by four the elements in the uranium series have mass numbers divisible by four with a remainder of two. The actinium series elements have mass numbers divisible by four with a remainder of three. It was not until the neptunium series was discovered that a decay series with a mass number divisible by four and a remainder of one was found. The neptunium decay series proceeds as follows, starting with the isotope plutonium-241 Pu-24l—> Am-24l Np-237 Pa-233 U-233 Th-229 Ra-225 Ac-225 Fr-221 At-217 Bi-213 Ti-209 Pb-209 Bi-209. 

F. Soddy, A. S. Russell, and K. Fajans independently predicted the existence of a new member of the uranium series of radioactive elements and that it would occupy the vacant place just below tantalum in the Va group of the periodic system. Protactinium, the patriarch of the actinium series of elements, was discovered in 1917 independently by Otto Hahn and Miss Lise Meitner, by K. Fajans, and by Frederick Soddy, John A. Cranston, and A. Fleck (47, 49, SO). 

The actinium series is very much like that of radium. In 1904 and 1905 Giesel and T. Godlewsld, while working independently, discovered the element actinium X, which is precipitated with the ferric hydroxide by adding an excess of ammonium carbonate solution to a solution containing actinium and iron (41, 44). 

The decay of 235U is also primarily by -decay through the actinium series (Fig. 8.15). 

Portion of the chart of the nuclides illustrating the decay of 235U to 207Pb. This decay series is often called the actinium series. 

Rn is formed by the alpha disintegration of 226Ra. Actinon, its isotope of mass number 219, is produced by alpha disintegration of 223 Ra (AcX) and is a member of the Actinium Series. Similarly, thoron, its isotope of mass number 220. is a member of the thorium senes. Since the name radon may be considered to be specific for the isotope of mass number 222 (from the radium series), the term emanation is sometimes used for element number 86 in general. Other isotopes of radon include those of mass numbers 209-218 and 221. 

This appears to have been the case with Curie, as I have argued elsewhere. [6] For Curie, knowing an element meant being able to produce it in fair amounts the concentration of elements was an important goal in itself, but it was also essential in order to the in-depth analysis of radioactive substances. She applied this policy to radium, polonium and to elements in the actinium series, though short lifetimes often prevented Curie and her coworkers to reach their goal no matter the industrial resources at their disposal. While this was a characteristic feature of Curie s work on radioactivity, this does not mean she was alone. To give another example In 1907 Otto Hahn had barely discovered mesothorium (MsTh, a mixture of MsThl, an... 

Both a 4n and a 4n + 3 series of heavy radioactive elements occur naturally. The 4n series is sometimes called the thorium series, since its long-lived parent is Th232 (half-life, 14,000,000,000 years), whereas the 4n + 3 series is the actinium series. The long-lived parent of the latter is U235 (half-life 707,000,000 years), but unlike the 4n + 2 series, one of its members is actinium (Ac227). Final members of both of these series are lead isotopes, Pb208 and Pb207. 

Similar equations describe the decays of radionuclide to radiogenic pb and of Th to 2° Pb. The decay of radionuclide (t, 2 0.72 x 10° a) gives rise to the actinium series, which ends in the stable 2° Pb after the emission of seven a ( He) decays and four 3 decays ... 

The great variety of radionuclides present in thorium and uranium ores are listed in Tables 4.1, 4.2 and 4.3. Whereas thorium has only one isotope with a very long half-life (- Th), uranium has two and giving ri.se to one decay scries for Th and two for U. In order to distinguish the two decay series of U, they were named after long-lived members of practical importance the uranium-radium series and the actinium series. The uranium-radium series includes the most important radium isotope ( Ra) and the actinium scries the most important actinium isotope ( Ac),... 

In the early stages of dating by nuclear methods, the measurement of He formed by a decay in the natural decay series (9, 6 and 7 He atoms in the uranium series, the thorium series and the actinium series, respectively) has been applied. The preferred method was the U/He method which allows dating of samples with very low concentrations of U of the order of 1 mg/kg. Helium produced by a decay is driven out by heating and measured by sensitive methods, e.g. by MS. However, it is difficult to ensure the prerequisites of dating by the U/He method neither " He nor a-emitting members of the decay series must be lost and no " He atoms must be produced by other processes such as decay of Th and spallation processes in meteorites. 

The uranium-235 series proceeds similarly and ends at lead-207. This series is sometimes called the actinium series. 

In the actinium series atomic numbers are given because the atomic weights are uncertain. 

Actinium is a member of a third radioactive seres, known as the actinium series, which originates in actino-uranium, an isotope of uranium I with a half-life period of 4 X io8 years. It occurs in all uranium minerals in a constant ratio to UI whatever the age. 

The immediate parent of actinium is protactinium or eka-tantalum, discovered independently by Hahn and by Soddy in 1917 it occupies the position between thorium and uranium left vacant by Mendel eff in his Periodic Table of 1869. loses an a-particle yielding actinium. At one time the actinium series was regarded as a branch of the uranium series. In old minerals the... 

The main source of terrestrial radiation is long-living isotopes of the uranium-radium series the thorium series ( Th) and the actinium series... 

FlC- 1-2, The three naturally occurring radioactive decay series and the man-made neptunium series. Although (which is the parent to the actinium series) and (which is the parent to the thorium series) have been discovered in nature, die decay series shown here begin with the most abundant Icmg-Uved nuclides. 

The actinium decay series consists of a group of nuclides whose mass number divided by 4 leaves a remainder of 3 (the 4n + 3 series). This series begins with the uranium isotope which has a half-life of 7.04 X 10 y and a specific activity of 8 X 10 MBq/kg. The stable end product of the series is ° Pb, which is formed after 7 a- and 4 /3-decays. The actinium series includes the most important isotopes of the elements protactinium, actinium, ftancium, and astatine. Inasmuch as U is a conqx>nmt of natural uranium, these elem ts can be isolated in the processing of uranium minerals. The longest-lived protactinium isotope, Pa (ti 3.28 X 10 y) has been isolated on the 100 g scale, and is the main isotope for the study of protactinium chemistry. Ac (t 21.8 y) is the longest-lived actinium isotope. 

Geiger and E. Marsden. Actinium-B had been discovered by Debierne (see p. 938), who called it actinium-A, and actinium-C by Rutherford and H. T. Brooks. Actinium-C and -C" were discovered by Marsden et al. Rutherford (see above) suggested that the actinium series begins with an isotope of uranium, actinouranium with an atomic weight of 235 or 239 (it is which occurs in small amounts in natural uranium). 

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