Uranium mass number range

In addition to the naturally occurring isotopes, several artificial short-lived uranium isotopes have been prepared, with mass numbers ranging from 227 to 240, but their short life precludes any natural occurrence. 

ISOTOPES There are 37 isotopes of radon. All are radioactive. None are stable. They range in mass numbers from Rn-196 to Rn-228. Their half-lives range from a few microseconds to 3.8235 days for Rn-222, which is the most common. It is a gas that is the result of alpha decay of radium, thorium, or uranium ores and underground rocks. 

Radium is element number 88, in which all of its isotopes are radioactive hence, what little radium is found on Earth is mostly as a trace element in uranium ores. The most common isotope has a mass number of 226 with a half-life of 1,604 years. The second longest-lived isotope is radium 228, with a half-life of 5.77 years. The other isotopes have much shorter half-lives ranging from microseconds to days. Radium is constantly being formed as part of the radioactive decay series of uranium and thorium. Because it decays so quickly, however, only minute quantities of radium ever exist at any one time. 

When pure, thorium is a silvery white metal. In air, it tarnishes slowly, becoming gray and finally black. Thorium has isotopes ranging in mass number from 210 to 237, all isotopes being radioactive. Much of the internal heat in the earth s crust has been attributed to thorium (and uranium). Thorium is a potential atomic fuel source, because bombardment of Th with slow neutrons yields the fissile isotope There... 

We have seen that the stablest nuclei are those of intermediate size (with mass numbers around 50). Nuclear fission and nnclear fusion are reactions in which nuclei attain sizes closer to this intermediate range. In doing so, these reactions release tremendous amounts of energy. Nuclear fission of uranium-235 is employed in nuclear power plants to generate electricity. Nuclear fusion may supply us with energy in the future. 

The number of neutrons in a nucleus does not affect the identity of the element but does affect its mass. Typically, the number of neutrons in a nucleus is similar to (and generally somewhat more than) the number of protons, but numbers of neutrons can vary by a few either way—hence the isotopes. Carbon, for instance, almost always has six neutrons in addition to its six protons, but isotopes with seven and eight protons are also known. The range of numbers of neutrons is greater in the south of the kingdom, as the proportion of neutrons needed to help bind these proton-rich nuclei together increases. At uranium, for instance, the 92 protons are accompanied by about 150 neutrons, with 146 being the most common value. 

In practice, a range of fission products with masses similar to krypton and barium are formed when uranium is irradiated with neutrons. This reaction is important, as it is used to produce nuclear power. There are two vital features that make this application possible first, the amount of energy liberated and, second, the number of neutrons produced. 

The mass spectrum generated with an ICP-MS is extremely simple (see Figure 1.1). Each elemental isotope appears at a different mass e.g. Al would appear at 27 amu) with a peak intensity directly proportional to the initial concentration of that isotope in the sample solution. A large number of elements ranging from lithium at low mass to uranium at high mass are simultaneously analysed, typically within 1-3 minutes. With ICP-MS, a wide range of elements in concentration levels from parts per thousand (ppt) to ppm level can be measured in a single analysis. 

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