Characteristic natural isotope mixture

In the human body strontium is assimilated in the same way as calcium and is incorporated together with calcium as a component of the skeletal material of the bones. These characteristics of strontium have no harmful effect on the organism but may lead to health problems if instead of the naturally occurring non-radioactive isotopic mixture the long-lived isotope strontium-90 (B"emitter, half-life 28 years), which is formed during... 

Natural gadolinium is a mixture of seven isotopes, but 17 isotopes of gadolinium are now recognized. Although two of these, 155Gd and 157Gd, have excellent capture characteristics, they are only present naturally in low concentrations. As a result, gadolinium has a very fast burnout rate and has limited use as a nuclear control rod material. 

The uranium isotopes often encountered in the radioanalytical chemistry laboratory are listed in Table 6.2. In natural uranium, the relative decay rates at equilibrium are 1.0 Bq 1.0 Bq and 0.045 Bq Emiched (containing relatively more and and depleted (relatively more U) combinations are also encountered, as are in neutron-irradiated mixtures and from some processes. These uranium isotopes emit alpha particles, characteristic 13-keV L X rays, and generally several weak gamma rays. Several isotopes have numerous minor alpha-particle or gamma-ray transitions that are not listed. 

Recall from Chapter 2 that the nucleus contains essentially all the atom s mass but is only about 10 times its radius (or 10 times its volume), making the nucleus incredibly dense about 10 g/mL. Protons and neutrons, the elementary particles that make up the nucleus, are called nucleons. A nuclide is a nucleus with a particular composition, that is, with specific numbers of the two types of nucleons. Most elements occur in nature as a mixture of isotopes, atoms with the characteristic number of protons of the element but different numbers of neutrons. Each isotope of an ele-... 

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