Uranium-actinium series

The 4n series - the thorium series The 4n + 1 series — the neptunium series The 4n + 2 series = the uranium-radium series The 4n + 3 series - the uranium-actinium series... 

The series of Radioactive disintegrations the uranium-radium series, the uranium-actinium series, the thorium series, and the neptunium series. The age of the earth. The fundamental particles electron, proton, positron, neutron, positive, negative, and neutral mesons, neutrino. The photon (light quantum) the energy of a photon, hv. Planck s constant. The wave-particle duality of light and of matter. The wavelengths of electrons. 

The uranium-actinium series, shown in Figure 20-7, is a similar series beginning with which occurs to the extent of 0.71% in natural uranium. It leads, through the emission of seven alpha particles and four beta particles, to the stable isotope -" Pb. 

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. 

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 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. 

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... 

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. 

This series (Figure 16.3) was so called because it was originally thought that actinium-227 was the parent element. However, actinium-227 decays too quickly for the series to persist for any length of time, and eventually uranium-235 was proved to be the true parent element. Uranium-235 is the less common naturally occurring isotope of uranium. The series ends with yet another stable lead isotope, lead-207, and the series formula is 4x + 3. 

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). 

Once it became clear that radioactive elements were decaying to new elements, which were themselves radioactive, a great deal of effort was expended in working out the decay sequences. In most cases the new elements were at first obtained in quantities too small to be weighed and were distinguished from each other only by the type of decay they exhibited and the rate at which the decay occurred. Three decay series were elucidated the uranium series proceeded through radium and terminated with the stable radium G the thorium series ended in the stable thorium D and the actinium series ended in actinium D. Between them, these series contained around 25 new radioelements. 

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