Radioactive Disintegration Series

These three series begin with the eiements uranium, thorium, and actinium. 

By using these series and the half-lives of their members, scientists have been able to approximate the age of certain geologic deposits. This approximation is done by comparing the amount of 9fU with the amount of Pb and other nuclides in the series that are present in a particular geologic formation. Rocks found in Canada and Finland have been calculated to be about 3.0 x 10 (3 billion) years old. Some meteorites have been determined to be 4.5 x 10 years old. 

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Radioactive Disintegration Series The series of spontaneous changes that take place starting from the parent element (which has unstable nucleus) till the formation of an element with stable nucleus is called... 

Decay product A nuclide resulting from the radioactive disintegration of a radionuclide and found as the result of successive transformations in a radioactive series. A decay product may be either radioactive or stable. 

Thorium undergoes radioactive disintegration through several decay steps ending by forming stable lead-208. The decay series involves six alpha and four beta emission steps. Radon-220 (thoron), an alpha emitter, is one of the disintegration products in the series. 

A radioactive element may be designated as being in a collateral senes. In addition to the three main natural and one artificial disintegration series of radioactive elements, each has been round to have at least one parallel or collateral series. The main series and the collateral series have different parents, but become identical in the course of disintegration, when they have a member in common. 

The radioactive decay of uranium and thorium results in the formation of a series of isotopes that are radiogenic by themselves and keep disintegrating into stable lead isotopes. These radioactive disintegrations are accompanied by the emissions of 4He atoms. Three such radioactive series exist ... 

The Uranium Series o Radioactive Disintegrations. When an alpha particle (He++) is emitted by an atomic nucleus the nuclear charge decreases by two units the element hence is transmuted into the element two columns to the left in the periodic table. Its mass number (atomic weight) decreases by 4, the mass of the alpha particle. 

The nature of radioactive disintegration within each of the four series—the emission of yS-particles, with mass nearly zero, or of a-parti-cles, with mass 4—is such that all the members of a series have mass numbers differing by a multiple of 4. The four series can hence be classified as follows n being integral) ... 

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. 

A radionuclide, upon undergoing disintegration of a particular type, yields a specified nuclide. The original radionuclide is called the parent and the decay product is called the daughter. The daughter may also be a radionuclide. A succession of nuclides, each of which transforms by radioactive disintegration into the next until a stable nuclide results, is called a radioactive series. Examples of such series are the uranium series and the thorium series. 

There is no difference between the principles governing natural and artificial radioactivity. The classical disintegration series stem from radionuclides with long half-lives, exceeding 10 years. Their decay is almost entirely by a- and /9-emissions. 

While studying radioactivity it was found thit hd obtained from the disintegration series of uranium hjs... 

The disintegration of a radioactive nucleus is often the beginning of a radioactive decay series, which is a sequence of nuclear reactions that ultimately result in the formation of a stable isotope. Table 23.3 shows the decay series of naturally occurring uranium-238, which involves 14 steps. This decay scheme, known as the uranium decay series, also shows the half-lives of all the products. 

Three isotopes of lead are the end products of the three natural disintegration series just considered. As these are inactive they accumulate in their radioactive mineral sources. 

Some nuclei cannot gain stability by a single emission. Consequently, a series of successive emissions occurs as shown for uranium-238 in A FIGURE 21.3. Decay continues until a stable nucleus—lead-206 in this case—is formed. A series of nuclear reactions that begins with an unstable nucleus and terminates with a stable one is known as a radioactive series or a nuclear disintegration series. Three such series occur in nature uranium-238 to lead-206, uranium-235 to lead-207, and thorium-232 to lead-208. 

SECTION 21.2 The neutron-to-proton ratio is an important factor determining nuclear stability. By comparing a nuclide s neutron-to-proton ratio with those in the band of stability, we can predict the mode of radioactive decay. In general, neutron-rich nuclei tend to emit beta particles proton-rich nuclei tend to either emit positrons or im-dergo electron capture and heavy nuclei tend to emit alpha particles. The presence of magic numbers of nucleons and an even number of protons and neutrons also help determine the stability of a nucleus. A nuclide may undergo a series of decay steps before a stable nuclide forms. This series of steps is called a radioactive series or a nuciear disintegration series. 

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