Nuclides isotopes

Isotopes—Nuclides having the same number of protons in their nuclei, and hence the same atomic number, but differing in the number of neutrons, and therefore in the mass number. Identical chemical properties exist in isotopes of a particular element. The term should not be used as a synonym for nuclide because isotopes refer specifically to different nuclei of the same element. 

Isotope Nuclides that have the same number of protons in their nucleus, and hence belong to the same element, but have different numbers of neutrons. 

Two recent developments of immunoassay, namely the use of free radicals and enzymes (M17, RIO) as markers instead of isotopic nuclides, can be expected to increase the scope and application of the technique. Both have already been applied to the detection and measurement of drugs in biological fluids but have not, so far, achieved the requisite specificity and precision necessary for clinical use. 

TABLE 21.1 Definitions of Atoms, Chemical Elements, Isotopes, Nuclides, and Isomers... 

An isotopically unmodified compound is one whose isotopic nuclides are present in the proportions that occur in nature. An isotopically modified compound has a nuclide composition that deviates measurably from that occurring in nature. 

The term nuclide implies an atom of specified atomic number (proton number) and mass number (nucleon number). Nuclides having the same atomic number but different mass numbers are called isotopic nuclides or isotopes. Nuclides having the same mass number but different atomic numbers are called isobaric nuclides or isobars. 

Nuclear reactions may lead to stable or unstable (radioactive) products. In general, (n, y), (n, p), and (d, p) reactions give radionuclides on the right-hand side of the line of p stability that exhibit decay, whereas (p, n), (d,2n), (n, 2n), (y, n), (d, n) and (p, y) reactions lead to radionuclides on the left-hand side of the line of p stability that exhibit p decay or electron capture (e). (n, y), (d, p), (n, 2n) and (y, n) reactions give isotopic nuclides, and these cannot be separated from the target nuclides by chemical methods, except for the application of the chemical effects of nuclear transformations which will be discussed in chapter 9. 

The chemical effects observed after neutron irradiation of ethyl iodide have found great practical interest, because they allow general application to various compounds and chemical separation of isotopic products of nuclear reactions. Above all, isotopic nuclides of high specific activity can be obtained by Szilard-Chalmers... 

With respect to chemical separation of isotopic nuclides from target nuclides after (n, y) reactions, changes of the valence state and of complexation are of special interest. Some examples are listed in Table 9.3. All nuclides produced by (n, y) reactions are found in appreciable amounts in lower valence states and free from com-plexing ligands, respectively. 

Isotopes. Nuclides having the same atomic number, that is, the same number of protons in the nucleus. Examples are r C and l C. 

Atomic number (Z) Mass number (A) Isotopes Nuclide Radioactive Beta particle Nuclear equation Alpha particle... 

Element Atomic weight Isotope (nuclide) Exact mass... 

Isotope—nuclide of an element having the same number of protons but a different number of neutrons, any of two or more forms of an element in which the weights differ by one or more mass units due to a variation in the number of neutrons in the nuclei. 

Element Atomic Weight Isotope (Nuclide) Exact Mass... 

Isotopes. Forms of the same element having identical chemical properties but differing in their atomic masses (because they have different numbers of neutrons in their respective nuclei) and nuclear properties. For example, hydrogen has three isotopes hydrogen, with a mass of 1 deuterium, with a mass of 2 and tritium, with a mass of 3. The first two are stable (nonradioactive), but tritium is a radioactive isotope. Nuclides have the same number of protons in their nuclei and hence the same atomic number, but differ in the number of neutrons and therefore in mass. Both isotopes of uranium, with masses of 235 and 238 units respectively, are radioactive (emit alpha particles), but their half-lives are different, releasing their radioactivity at a different rate. Furthermore, uranium 235 is readily fissionable by neutrons of all energies, while uranium 238 is not. 

The Atomic Energy Act of 1954 defines special nuclear materials (or SNM) as U, plutonium, or vanium enriched in These are the fissile isotopes (nuclides that undergo fission with high probability when irradiated with neutrons of any energy) that can be... 

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is also used to study nuclear materials. Commonly, samples are introduced into an ICP-MS via an aerosol. However, LA has become the sample introduction technique of choice for solid samples and those samples that cannot be easily aero-solubilized [100]. Nanosecond LA coupled to an ICP-TOF-MS can rapidly screen nuclear and nonnuclear solid samples for a wide array of nuclides and isotopes (nuclides of the same element) [101]. LA-ICP-MS is also used to analyze uranium oxide [102-103] these studies determine the ratios of U-235, U-236, and U-238 isotopes in the sample from microgram sample quantities. Isotopic ratio calculations are essential to determine if the sample is natural or of human origin. 

Imperfect tracers are often used when labeling of a specific chemical site is inappropriate with isotopic nuclides. Imperfect tracers are widely used to label gas streams with inert gases ( Kr, Ar, Xe), water with dissolved anionic tracers ( "Br, l, Na), hydrocarbon fuels with dis-... 

ISOTOPES Nuclides having the same atomic number but different mass numbers. 

Isotope Nuclide Atomic mass Part of total hydn n in nature % Half life... 

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