Alpha elements abundance

Second, lithium, beryllium, and boron have very low abundances. These elements are, for the most part, not made in stars and were not made efficiently in the Big Bang. They are produced via cosmic ray interactions. Nuclei of heavier atoms, when hit by fast moving protons or other nuclei, can break into pieces, including protons, neutrons, alpha particles, and heavier fragments. Some of these fragments are lithium, beryllium, and boron nuclei. 

Secondary nuclei tend to be neutron-rich isotopes of the alpha elements (O, Ne, Mg, Si, S, Ar, and Ca). To make neutron-rich isotopes in stars requires a source of neutrons, and this in turn requires that the gas in bulk contain more neutrons than protons by a small amount. This requires that the star contain an abundant... 

Boron [7440-42-8] B, is unique in that it is the only nonmetal in Group 13 (IIIA) of the Periodic Table. Boron, at wt 10.81, at no. 5, has more similarity to carbon and siUcon than to the other elements in Group 13. There are two stable boron isotopes, B and B, which are naturally present at 19.10—20.31% and 79.69—80.90%, respectively. The range of the isotopic abundancies reflects a variabiUty in naturally occurring deposits such as high B ore from Turkey and low °B ore from California. Other boron isotopes, B, B, and B, have half-Hves of less than a second. The B isotope has a very high cross-section for absorption of thermal neutrons, 3.835 x 10 (3835 bams). This neutron absorption produces alpha particles. 

All reactor-produced plutonium contains a mixture of several plutonium isotopes. The continuous decay of 241pu (14.8 year half-life) is the source of 241/. jhis isotope decays by alpha emission with the simultaneous emission of 60 kilovolt gamma rays in 80% abundance. In order to minimize personnel exposure, this element is removed from the metal prior to fabrication. 

Uranium is a heavy element that has a number of isotopes (see Textbox 16). Minerals and rocks as well as human made materials such as ceramics and glass often contain trace amounts of uranium as impurities. The most abundant isotope of this element, uranium-238, is radioactive and most of it decays into thorium-234 by the emission of alpha particles ... 

The first papers in this field suggested that the overall alpha abundances found in the most metal-poor dSph stars are not similar to those found in the halo. However, a more detailed analysis of the individual elements including corrections for differences in log gf values has shown that the O and Mg abundances are consistent with those found in the MW halo, while the Ca and Ti abundances are systematically lower than those in the MW halo, see figure 1, 2 and 6 in Shetrone (2004). This can also be seen in Figure 1 which shows that the most metal-poor Sculptor stars have [Ca/Fe] ratios less than 0.2 dex while the halo median at this metallicity is roughly 0.15 dex larger. 

Radon-222 also undergoes radioactive decay and has a radioactive half-life of 3.8 days. Radon-220 and -219 have half-lives measured in seconds and are not nearly as abundant as Radon-222. Thus the discussion of radon health effects here centers on Radon-222. Radon-222 decays into radon daughters or progeny, which are radioactive elements. Two of these (polonium-218 and polonium-214) emit alpha particles (high-energy, high-mass particles, each consisting of two protons and... 

Symbol Ce atomic number 58 atomic weight 140.115 a rare-earth metal a lanthanide series inner-transition /-block element metaUic radius (alpha form) 1.8247A(CN=12) atomic volume 20.696 cm /mol electronic configuration [Xe]4fi5di6s2 common valence states -i-3 and +4 four stable isotopes Ce-140 and Ce-142 are the two major ones, their percent abundances 88.48% and 11.07%, respectively. Ce—138 (0.25%) and Ce—136(0.193%) are minor isotopes several artificial radioactive isotopes including Ce-144, a major fission product (ti 284.5 days), are known. 

The Mars Pathfinder rover carried an Alpha Proton X-ray Spectrometer (APXS), and the two Mars Exploration Rovers (MER - Spirit and Opportunity) carried Alpha Particle X-ray Spectrometers (also called APXS, but in this case more precise versions of the Pathfinder instrument, though without the ability to monitor protons for light element analyses). These instruments contained radioactive curium sources (Fig. 13.16) whose decay produced a-particles, which irradiated target rocks and soils. The resulting characteristic X-rays provided measurements of major and minor element abundances. The MER rovers also carried Mossbauer spectrometers, which yielded information on iron oxidation state. 

Because helium forms no compounds and is almost absent in the Earth s atmosphere, it was unknown for a long time. The first clue leading to its discovery was an unidentified yellow emission line in the solar chromospheric spectrum observed by French astronomer Pierre Janssen during an eclipse of the Sun in 1868. Lockyer named the unknown element helium for the Greek sun god, helios. Subsequendy it was discovered to be rather abundant in radioactive rocks, where it is trapped after emission from uranium series alpha decays. Ramsay and Soddy showed that the alpha rays were helium atoms whose electrons had been stripped away. In his biography of Lord Rutherford, A. S. Eve wrote ... 

The Caabundance has been studied in stars by optical spectra. Because 40 Ca dominates the spectra of Ca in stars, and especially because 4°Ca is a primary alpha nucleus, the galactic evolution of 4°Ca is the same as the observed galactic evolution of calcium elemental abundance. As nucleosynthesis progressed in the galaxy the Ca/H abundance... 

Bismuth (Z = 83) is the heaviest stable element in group 15 (VA) of the periodic table (see Periodic Table Trends in the Properties of the Elements). The Bi isotope, which is 100% abundant, has a 9/2 nuclear spin. Bi, an alpha emitter is used in nuclear medicine as a radiotherapeutic agent. Bismuth has two stable oxidation states Bi(V), corresponding to complete loss of the valence electrons, and Bi(III), a lower oxidation state that retains two valence electrons. Both oxidation states are diamagnetic. The latter is more stable and more common since Bi(V) has a large reduction potential ... 

A few informative properties of life come from easy category distinctions, such as the fact that all known life makes essential use of carbon and carbon-oxygen-nitrogen molecules in liquid water solution. The seemingly trivial observation that such carbaquist chemistry is ruled out if astrophysical carbon abundance lies below a certain threshold enabled Hoyle [1] to predict the 7.6 MeV carbon-12 ( C) nuclear resonance with remarkable precision because the discovery of the triple-alpha reaction synthesis of in stars happens to be a bottleneck for stellar nucleosynthesis of all the heavy elements. The pragmatic information in this prediction is easy to measure because it guided experimental characterization of nuclear structure where the existing computational capabilities could not. Similar sensitive dependence of the physical state of water has been used to define a habitable zone in planetary physics [10], which is not predictive in the same sense as carbon abundance (we already knew where the earth s orbit lies), but which creates a useful filter in the search for extraterrestrial life. 

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