Nuclear decay series

Mass number parity (A) Decay series name Header radionuclide (r, and ) Natural isotopic abundance Specific activity of parent radionuclide ( ) End stable nuclide ( ) Gaseous radioelement (emanation, old symbol) 

Important note ( ) Specific activity of the parent radionuclide alone without considerin decaying radionuclides in secular equilibrium with it. ( ) The three stable lead isoto daughters of the three natural decay series, and hence are called radiogenic lead isoto] the naturally occurring lead isotope Pb. the activity of each )es are the ultimate jes by contrast with 

Radionuclide Historical name (Symbol) Atomic mass (M,/u) Half-life (.TJ Radioactivity  

Radionuclide Historical name Atomic mass Half-life Radioactivity  

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Nuclear decay series A series of radioactive decays that lead from a large unstable nuclide, such as uranium-238, to a stable nuclide, such as lead-206. 

Some reactions, including both chemical reactions and nuclear decays, occur in a series of steps. We can look at the sequence of reactions A B C and study the changes in the numbers of the three species as the reaction series proceeds. 

We first write conventional nuclear reactions for each step in the decay series. 

A particular isotope may undergo a series of nuclear decays until finally a stable isotope forms. For example, radioactive U-238 decays to stable Pb-206 in 14 steps, half of these are alpha emissions and the other half are beta emissions. 

FIGURE 22.6 The decay series from 2j U to 2 Pb. Each nuclide except for the last is radioactive and undergoes nuclear decay. The leftpointing, longer arrows (red) represent a emissions, and the right-pointing, shorter arrows (blue) represent /3 emissions. 

KEY CONCEPT PROBLEM 22.10 The following series has two kinds of processes one represented by the shorter arrows pointing right and the other represented by the longer arrows pointing left. Tell what kind of nuclear decay process each arrow corresponds to, and identify each nuclide A-E in the series ... 

Radioactive decay occurs because of nuclear instability, with the end result of decay being stability. If this stability is not achieved by the first nuclear transformation, then more transformations occur. This set of transformations is called a decay series, as shown in Figure 14.4. 

When the nucleus of a radioactive atom disintegrates, it emits various particles and so changes its own composition. When an alpha particle is lost then a new element is formed, which is two places to the left in the periodic table. When a beta particle is lost then a new element is formed which is one place to the right in the periodic table. Therefore, by a series of losses of alpha and beta particles, the element progressively changes. This is called decay , and the pattern it follows until a stable nuclear arrangement is reached (usually when the element lead is formed) is called the decay series (see Chapter 12). 

The element francium is formed in the natural radioactive decay series and in nuclear reactions. All its isotopes are radioactive with short half-lives. The ion behaves as would be expected from its position in the group. 

All isotopes of radium are radioactive, the longest-lived isotope being 226Ra (a —1600 years). This isotope is formed in the natural decay series of 238U and was first isolated by Pierre and Marie Curie from pitchblende. Once widely used in radiotherapy, it has largely been supplanted by radioisotopes made in nuclear reactors. 

There is no stable isotope of polonium. The isotope 210Po(a, 138.4d) occurs in U and Th minerals as an intermediate in the radioactive decay series, and was discovered by M. S. Curie in 1898. The only practical source of polonium (in gram quantities) is from nuclear reactors by the process... 

The physical properties of uranium and uranium compounds important in the nuclear fuel cycle and defense programs are listed in Table 3-2. The percent occurrence and radioactive properties of naturally occurring isotopes of uranium are listed in Table 3-3. The two decay series for the naturally occurring isotopes of uranium are shown in Table 3-4. 

It was named in analogy to uranium after the planet Neptune. The Np isotope with the longest half-life (O/2 2.144 10 y) is Np, the mother nuclide of the (artificial) decay series with A = An + (section 4.1). It is produced in nuclear reactors ... 

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