Nonradioactive isotope

Neutron Activation Analysis Few samples of interest are naturally radioactive. For many elements, however, radioactivity may be induced by irradiating the sample with neutrons in a process called neutron activation analysis (NAA). The radioactive element formed by neutron activation decays to a stable isotope by emitting gamma rays and, if necessary, other nuclear particles. The rate of gamma-ray emission is proportional to the analyte s initial concentration in the sample. For example, when a sample containing nonradioactive 13AI is placed in a nuclear reactor and irradiated with neutrons, the following nuclear reaction results. 

Isotope Dilution Another important quantitative radiochemical method is isotope dilution. In this method of analysis a sample of analyte, called a tracer, is prepared in a radioactive form with a known activity. Ax, for its radioactive decay. A measured mass of the tracer, Wf, is added to a sample containing an unknown mass, w, of a nonradioactive analyte, and the material is homogenized. The sample is then processed to isolate wa grams of purified analyte, containing both radioactive and nonradioactive materials. The activity of the isolated sample, A, is measured. If all the analyte, both radioactive and nonradioactive, is recovered, then A and Ax will be equal. Normally, some of the analyte is lost during isolation and purification. In this case A is less than Ax, and... 

Few of the naturally occurring elements have significant amounts of radioactive isotopes, but there are many artificially produced radioactive species. Mass spectrometry can measure both radioactive and nonradioactive isotope ratios, but there are health and safety issues for the radioactive ones. However, modem isotope instmments are becoming so sensitive that only very small amounts of sample are needed. Where radioactive isotopes are a serious issue, the radioactive hazards can be minimized by using special inlet systems and ion pumps in place of rotary pumps for maintaining a vacuum. For example, mass spectrometry is now used in the analysis of Pu/ Pu ratios. 

A few natural isotopes are radioactive. Of the three isotopes of hydrogen, only that of mass 3 (tritium) i.s radioactive. Radioactive isotopes can be examined by other instrumental means than mass spectrometry, but these other means cannot see the nonradioactive isotopes and are not as versatile as a mass Spectrometer. 

Elements with multiple stable isotopes may produce several radioisotopes that can be measured to assure the accuracy of the analysis. For example, Zn has five stable isotopes. The isotope Zn will produce the radioisotope Zn, and Zn will produce the radioisotope Zn. Both of these radioisotopes can provide an independent measurement of the Zn concentration and therefore can be used to check the consistency and quality of the analysis. On the other hand, Zn will produce Zn, which is nonradioactive and therefore cannot be used in NAA. 

C22-0124. A small amount of NaBr containing the radioactive isotope sodium-24 is dissolved in a hot solution of sodium nitrate containing the naturally occurring nonradioactive isotope sodium-23. The solution is cooled, and sodium nitrate precipitates from the solution. Will the precipitate be radioactive Explain your answer. 

Isotopic tracers are not exclusively radioactive. For instance, is a nonradioactive element that is suitable for a nonradioactive labeling technique. 

In some cases, isotope enrichment, particularly of stable and nonradioactive isotopes, is used to follow a particular element through the environment or through biological systems. The advantage of stable isotopes is that they are not radioactive and thus are easier to handle and dispose. 

It is critical when performing quantitative GC/MS procedures that appropriate internal standards are employed to account for variations in extraction efficiency, derivatization, injection volume, and matrix effects. For isotope dilution (ID) GC/MS analyses, it is crucial to select an appropriate internal standard. Ideally, the internal standard should have the same physical and chemical properties as the analyte of interest, but will be separated by mass. The best internal standards are nonradioactive stable isotopic analogs of the compounds of interest, differing by at least 3, and preferably by 4 or 5, atomic mass units. The only property that distinguishes the analyte from the internal standard in ID is a very small difference in mass, which is readily discerned by the mass spectrometer. Isotopic dilution procedures are among the most accurate and precise quantitative methods available to analytical chemists. It cannot be emphasized too strongly that internal standards of the same basic structure compensate for matrix effects in MS. Therefore, in the ID method, there is an absolute reference (i.e., the response factors of the analyte and the internal standard are considered to be identical Pickup and McPherson, 1976). 

Thulium is relatively scarce and expensive, which hmits its commercial uses. Thulium-170, which is a radioactive isotope of thuhum produced by fission in nuclear reactors, can be used as small, portable X-ray sources. It also has limited use as an alloy metal with other metals and has experimentally been used in lasers. (Note Of all the isotopes of thuhum, only thuhum-169 is stable and nonradioactive.)... 

Why do some nuclei undergo radioactive decay while others do not Why, for instance, does a carbon-24 nucleus, with six protons and eight neutrons, spontaneously emit a /3 particle, whereas a carbon-23 nucleus, with six protons and seven neutrons, is stable indefinitely Before answering these questions, it s important to define what we mean by "stable." In the context of nuclear chemistry, we ll use the word stable to refer to isotopes whose half-lives can be measured, even if that half-life is only a fraction of a second. We ll call those isotopes that decay too rapidly for their half-lives to be measured unstable, and those isotopes that do not undergo radioactive decay nonradioactive, or stable indefinitely. 

Of the 264 nonradioactive isotopes, 207 have an even number of neutrons in their nuclei. Most nonradioactive isotopes (156) have even numbers of both protons and neutrons, 51 have an even number of neutrons but an odd number of protons, and only 4 have an odd number of both protons and neutrons (Figure 22.4). 

A close-up look at a segment of the band of nuclear stability reveals some more interesting trends (Figure 22.5). One trend is that elements with an even atomic number have a larger number of nonradioactive isotopes than do elements with an odd atomic number. Tungsten (Z = 74) has 5 nonradioactive isotopes and osmium (Z = 76) has 7, for example, while their neighbor rhenium (Z = 75) has only 1. 

FIGURE 22.4 Numbers of nonradioactive isotopes with various even/odd combinations of neutrons and protons. The majority of nonradioactive isotopes have both an even number of protons and an even number of neutrons. Only 4 nonradioactive isotopes have both an odd number of protons and an odd number of neutrons. 

Significant concentrations of contaminant radium may be submicromolar. Therefore, radiochemical separations are commonly employed that make use of a carrier, a nonradioactive element with chemical properties similar to those of radium. For radium, barium is the element of choice, and radium is coprecipitated from solution with barium sulfate, BaSCH Correction for losses in the precipitation procedure may be made by adding a tracer consisting of an isotope of radium not expected in the sample and noting its recovery at the end of the analytical procedure. The isotope radium- 223 can be used for this purpose. 

Radioactive dating is a means of determining the age of a dead plant or animal by comparing the amount of a radioactive isotope in it with the amount of the same radioactive isotope in a living organism. Carbon-14 is often the isotope used for this purpose. Most carbon atoms are the nonradioactive carbon-12 isotope. The radioactive carbon-14 isotope is formed in the atmosphere as a result of random neutron capture, as shown here ... 

This technique is about 1000 times more sensitive than infrared and magnetic resonance spectroscopy, outlined later. It can also be used to detect different masses of radioactive and nonradioactive isotopes of elements. It can distinguish between the carbon 12 and 13 isotopes and also the oxygen 16 and 18 isotopes. By... 

Each radioactive isotope has a similar breakdown pattern before it ends up some millions of years later as a stable, nonradioactive isotope, usually lead. There are a few different series like the one shown. 

Explain the difference between iodine 123 and 131 in both the nuclear arrangement of protons and neutrons and the difference in the break-down of the nucleus. The usual nonradioactive isotope of iodine is I 127. If 131 iodine gives off one beta particle what new element is formed ... 

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