Neutron-rich isotopes, 6-decay half-lives

Pu. The isotope Pu is the longest-lived of the plutonium- isotopes, with a half-life of 8 X 10 years. It can be produced by neutron absorption in Pu, but because of the short half-life and low concentration of Pu only minute quantities of Pu, of the order of 10" percent, are present in reactor-produced plutonium [K2]. Small quantities of Pu, as well as Pu and Pu, are present in the residues from nuclear explosions, resulting from the decay of the neutron-rich uranium isotopes and formed by multiple neutron capture in the high neutron... 

Al-26 comes in two forms -- one with a 6.4 second half-life and one with a 7 million year half-life. Some radioisotopes have three different half-lives. So, for radioactive isotopes, we sometimes have to add to our symbol to tell which decay mode we mean. In the case of Al-26, the 6.4 second activity is a "higher energy state" and is called Al-26m. In class we will discuss decay schemes of radioisotopes we encounter at UWNR are produced by absorbing a neutron in a stable element and are "neutron rich" — which... 

Carbon exists in five isotopic forms. That is to say there are atoms of carbon with five different nuclear characteristics, specifically with different numbers of neutrons. These variations are denoted as carbon-11 (C-11), carbon-12 (C-12), carbon-13 (C-13), carbon-14 (C-14) and carbon-15 (C-15) in which the numbers of neutrons vary ftom 5 to 9 respectively. Of these isotopes, C-12 and C-13 are stable while the others are imstable and radioactive. In order to achieve stability, radioactive decay occurs involving the emission of particles from the nucleus. This occms at a constant rate for each isotope for C-11 the half-life, i.e. the time required for half the original number of atoms to decay is 20.3 minutes, for C-15 it is 2.5 seconds and for C-14 it is 5730 years. The long half life of the latter isotope allows it to be used as a means of estimating the age of carbon-rich substances that have been preserved through bmial in enviromnents that prohibit decomposition. The approximate age is determined by comparing the amount of radioactive carbon in the preserved sample with that in a modem sample. While the physical properties of the isotopes vary in this way, their chemical properties are the same, as reflected by their atomic munber of six. 

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