Abundance of the Elements

A major example of isotope-dilution analysis lies in the procedure itself, which does not require any quantitative isolation of the elements being investigated. The relation between the abundance of the element under investigation and the spike is such that, once the spike has been intimately mixed with the sample, any losses of sample have no effect on the result (Figure 48.14). 

Percentage of meteorites seen to fall. Chondrites. Over 90% of meteorites that are observed to fall out of the sky are classified as chondrites, samples that are distinguished from terrestrial rocks in many ways (3). One of the most fundamental is age. Like most meteorites, chondrites have formation ages close to 4.55 Gyr. Elemental composition is also a property that distinguishes chondrites from all other terrestrial and extraterrestrial samples. Chondrites basically have undifferentiated elemental compositions for most nonvolatile elements and match solar abundances except for moderately volatile elements. The most compositionaHy primitive chondrites are members of the type 1 carbonaceous (Cl) class. The analyses of the small number of existing samples of this rare class most closely match estimates of solar compositions (5) and in fact are primary source solar or cosmic abundances data for the elements that cannot be accurately determined by analysis of lines in the solar spectmm (Table 2). Table 2. Solar System Abundances of the Elements ... 

Various estimates of the universal abundances of the elements have been made and, although these sometimes differ in detail for particular elements, they rarely do so by more than a factor of 3 (10 ) on a scale that spans more than 12 orders of magnitude. Representative values are plotted in Fig. 1.1, which shows a number of features that must be explained by any satisfactory theory of the origin of the elements. For example ... 

Figure 1.1 Cosmic abundances of the elements as a function of atomic number Z. Abundances are expressed as numbers of atoms per 10 atoms of Si and are plotted on a logarithmic scale. (From A. G. W. Cameron, Space Sci. Rev. 15, 121-46 (1973), with some updating.)...

The following types of nuclear reactions have been proposed to account for the various types of stars and the observed abundances of the elements ... 

The nuclei of some elements are stable, but others decay the moment they are formed. Is there a pattern to the stabilities and instabilities of nuclei The existence of a pattern would allow us to make predictions about the modes of nuclear decay. One clue is that elements with even atomic numbers are consistently more abundant than neighboring elements with odd atomic numbers. We can see this difference in Fig. 17.11, which is a plot of the cosmic abundance of the elements against atomic number. The same pattern occurs on Earth. Of the eight elements present as 1% or more of the mass of the Earth, only one, aluminum, has an odd atomic number. 

The composition of the Earth was determined both by the chemical composition of the solar nebula, from which the sun and planets formed, and by the nature of the physical processes that concentrated materials to form planets. The bulk elemental and isotopic composition of the nebula is believed, or usually assumed to be identical to that of the sun. The few exceptions to this include elements and isotopes such as lithium and deuterium that are destroyed in the bulk of the sun s interior by nuclear reactions. The composition of the sun as determined by optical spectroscopy is similar to the majority of stars in our galaxy, and accordingly the relative abundances of the elements in the sun are referred to as "cosmic abundances." Although the cosmic abundance pattern is commonly seen in other stars there are dramatic exceptions, such as stars composed of iron or solid nuclear matter, as in the case with neutron stars. The... 

Table 2-1 Solar abundances of the elements (atoms/lO atoms of Si)...

The natural occurrence of the group-IIA elements ranges from common to rare e.g., Ca is 5th in the order of atomic abundance of the elements in the earth s crust. Mg is 7th, Ba and Sr are 21st and 22nd, respectively, and Be is 32nd . Radium is of extremely limited availability. It does occur naturally, although it has neither stable nor long-lived radioaetive isotopes it is found in association with U, since ll/2... 

Fig. 1.5. Comparison of crustal with whole-Earth abundances of the elements. Elements high up in this plot are enriched in the crust relative to the Earth as a whole ones low down are depleted and concentrated in the inner parts of the Earth. (Reproduced with permission from P.A.

All chemistry is limited by the abundance of the elements, restricted to 90 in total (two of the natural 92 have disintegrated completely). The properties of the elements are correlated in fixed Groups and Periods of the Periodic Table. 

The environmental impact of tin is appreciable, as it is one of the three most enriched metals—only lead and tellurium precede—in the atmospheric particular matter, as compared with the abundance of the element in the earth crust (2.2 ppm). Tin releases to the environment can be methylated by aquatic organisms, yielding organometallic species of toxicity comparable to that of methylated mercury5. 

E. Anders and N. Grevesse. Abundances of the Elements—Meteoritic and Solar, Geochimica et Cosmochimica Acta, 53(1989) 197-214. 

Anders E, Grevesse N (1989) Abundances of the elements meteoritic and solar. Geochim Cosmochim Acta 53 197-214... 

Chemical Element Balance. To help resolve this dilemma, the results of a simple chemical element balance based on Ca and K are useful. The calculations were performed separately for each of the 36 vane samples collected, so a distribution of the results could be presented. The input data for these calculations included the mean abundances of the elements in the source materials (local bulk soil and road dust)... 

Table 1) and the aerosol element abundances measured in the 36 Individual vane samples. The distributions of crustal element abundances in aerosols were shown in Figures 6-11 along with the respective abundances of the elements in the source materials. 

Anders, E. and Ebihara, M., 1982. Solar-system abundances of the elements. Geochim. Cosmochim. Acta, 46 2363-2380. 

During World War II, Hans Suess (1909-93) was part of a team of German scientists working on heavy water. In 1950, he immigrated to the United States. His work with Urey on nucleosynthesis and the abundances of the elements is a cornerstone of cosmochemistry. In 1965, along with Heinrich Wanke, he proposed that the extremely high noble gas contents... 

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