Beta-particle emission

Briefly describe radioactive transformations, particularly as they apply to beta particle emissions. 

Lead-210 has a half-life of 20.4 years. This isotope decays by beta particle emission. A counter registers 1.3 X 104 disintegrations in five minutes. How many grams of Pb-210 are there ... 

Beta particle emission results in the lowering of the neutron-to-proton ratio. 

In 1899 he identified two forms of radioactivity, which he called alpha and beta particles. As we saw earlier, he deduced that alpha particles are helium nuclei. Beta particles are electrons - but, strangely, they come from the atomic nucleus, which is supposed to be composed only of protons and neutrons. Before the discovery of the neutron this led Rutherford and others to believe that the nucleus contained some protons intimately bound to electrons, which neutralized their charge. This idea became redundant when Chadwick first detected the neutron in 1932 but in fact it contains a deeper truth, because beta-particle emission is caused by the transmutation ( decay ) of a neutron into a proton and an electron. 

Figure 4.1 Beta particle emission from thin and thick radioactive samples.

Look up the pertinent information to calculate the beta particle emission rate per gram of KC1. Compare your value to the estimated rate of 14 beta particles/s-g of KC1. 

The two fission-produced radio-strontium isotopes of interest in environmental samples are 90Sr and 89Sr. Sr-90 has a fission yield of 5.8 %, a half-life is 28.78 a, and the radioactive daughter 90Y with a half life of 2.67 d, to which it decays by beta-particle emission. Sr-89 has a fission yield of 4.7%, a half life of 50.52 d, and decays to the stable daughter89 Y. The decay schemes given in Figure 13.1 show that these two radio-strontium isotopes for practical purposes can only be measured by beta-particle counting. 

There are three main types of radioactive decay alpha particle emission, beta particle emission, and the emission of gamma radiation. When an unstable isotope undergoes radioactive decay, it produces one or more different isotopes. We represent radioactive decay using a nuclear equation. Two rules for balancing nuclear equations are given below. 

Q mil Alpha or beta particle emission from a radioactive nucleus is often, but not always, accompanied by gamma rays. Why does the presence of gamma rays not affect how a nuclear equation of this type is balanced ... 

Beta particle emission occurs when an ordinary electron is ejected from tlie nucleus of an atom. The electron (e) appears when a neutron (n) is transformed into a proton witiiin tlie nucleus. 

Beta particle emission occurs when an ordinaiy elearon is ejected from the nucleus of an atom. 

Beta particle emission—A neutron turns into a proton and an electron. The new proton stays in the nucleus and the electron is emitted from the atom, and the electron is called a heta particle. Another subatomic particle, known as an antineutrino, is also produced. An example is the decay of carhon-14 into nitrogen. 

Beta-particle emission Ifi") The nucleus emits a negativecl -Iron when a neutron changes to a proton. A y-ray may vr tiu) not accompany the emission of a fi panicle. 

Thus, beta emission results in an increase of one in the number of protons (the atomic number) and a decrease of one in the number of neutrons, with no change in mass number. Examples of beta particle emission are... 

Beta-particle emission leads to an increase in the number of protons in the nnclens and a simultaneous decrease in the nnmber of nentrons. Some examples are... 

Beta particles A beta particle is a very fast-moving electron that is emitted when a neutron in an unstable nucleus converts into a proton. Beta particles are represented by the symbol (3 or e. They have a 1 — charge. Their mass is so small compared with the mass of nuclei involved in nuclear reactions that it can be approximated to zero. Beta radiation consists of a stream of fast-moving electrons. An example of the beta decay process is the decay of iodine-131 into xenon-131 by beta-particle emission, as shown in Figure 24.4. Note that the mass number of the product nucleus is the same as that of the original nucleus (they are both 131), but its atomic number has increased by 1 (54 instead of 53). This change in atomic number occurs because a neutron is converted into a proton, as shown by the following equation. 

Positron emission occurs only when the energy difference between the parent radionuclide and the products exceeds 1.02 MeV (the energy equivalent of the sum of the masses of an electron and a positron). The atom s recoil, as for beta-particle emission, is a few electron volts. At lesser energy differences, a proton in the nucleus can be converted to a neutron by electron capture, i.e., the capture by the nucleus of an atomic electron from, most probably, an inner electron shell (see discussion below of CEs). The process of electron capture parallels positron emission and may occur in the same isotope. It is accompanied by emission of a neutrino and characteristic X rays due to the rearrangement of atomic electrons. Electron capture may also be signaled by the subsequent emission of gamma rays. Examples of these decays are given in Sections 9.3.4 and 9.3.6. 

Alternative 1 consists of measuring the strontium precipitate as soon as possible (within a few hours) after yttrium separation, and repeating the measurement after 2-4 weeks. As shown by the equations in Table 6.5, the first value consists of beta particles from Sr and °Sr, with a small contribution from the recently separated °Y. The latter is the calculable fraction Disoyrelative to the °Sr beta-particle activity. The second value consists of the same contributors, except that the Sr beta-particle emission rate has decreased according to its known half-life, while the °Y emission rate has increased to become almost the same as that for °Sr,... 

The decay scheme of the naturally occurring radionuclide (see Fig. 9.6) is 89.1% by beta-particle emission, 10.9% by electron capture, and 0.001% by positron decay. The 1311-keV maximum-energy beta-particle decay is to the ground state of " °Ca. Electron-capture decay is followed instantaneously by emission of a 1461-keV gamma ray from the excited state of °Ar to its ground state. Electron capture decay to the ground state is 0.2% per disintegration. 

The naturally occurring radioactive decay series that begins with IfU stops with formation of the stable Pb nucleus. The decays proceed through a series of alpha-particle and beta-particle emissions. How many of each type of emission are involved in this series ... 

A radioactive decay series that begins with oTh ends with formation of the stable nuclide Pb. How many alpha-particle emissions and how many beta-particle emissions are involved in the sequence of radioactive decays ... 

The mass number of a nucleus is unchanged after beta-particle emission, (a) True, (b) False. 

The art of good sample preparation is the ability to detect beta-particle emissions efficiently and reproducibly with the minimum of preprocessing. 

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