Abundance table

Tables of abundance factors have been calculated for all combinations of C, H, N, and O up to mass 500 (J. H. Beynon and A. E. Williams, Mass and Abundance Tables for Use in Mass Spectrometry, Elsevier, Amsterdam, 1963).

Beynon A.E. Williams, Mass and Abundance Tables for Use in Mass Spectrometry , Elsevier,... 

D.O. Schissler, Mass and Abundance Tables , Vols 1—III, Shell Development Co, Emeryville,... 

Multi-Element Analytical Scheme The 76 elements analyzed include 39 elements originally analyzed in the RGNR Projects, and 37 new elements. The analytical scheme is based largely on ICPMS, ICPAES and XRF, supplemented with other techniques (Table 1). The lower levels of detection of all elements are less than their crustal abundances (Table 2). 

So far we have treated the X-f1 and the X-f2 elements separately, which is not how they are encountered in most analytes. The combination of C, H, N and O with the halogens F, Cl, Br and I covers a large fraction of the molecules one usually has to deal with. When regarding H, O and N as X elements, which is a valid approximation for not too large molecules, the construction of isotopic patterns can be conveniently accomplished. By use of the isotopic abundance tables of the elements or of tables of frequent combinations of these as provided in this chapter or... 

Today we possess an abundance table of elements and isotopes characterising our local galactic environment, viz. the Solar System. We may draw several... 

Fig. 4.1. Abundance table of elements in the Solar System. The main features of the abundance distribution are as follows (1) the hydrogen (Z = 1) peak, shouldered by helium (Z = 2) the precipitous gorge separating helium and carbon (Z = 6) ...

After going through this exercise in pure spontaneity, let us carry out a harsher analysis of our fundamental data. Abundances in the Solar System reveal trends that directly reflect not the chemical or atomic properties of elements, but rather the characteristics of the nuclei of those elements. The key to understanding the abundance table thus lies in nuclear physics." ... 

We shall return to these mechanisms for creating ever more elaborate nuclei. But first, let us glance back at the abundance table, for it would be an oversight not to mention the rich nuggets of information that lie hidden in meteorite studies. 

Fig. 5.5. Decomposition of Solar System abundances into r and s processes. Once an isotopic abundance table has been established for the Solar System, the nuclei are then very carefully separated into two groups those produced by the r process and those produced by the s process. Isotope by isotope, the nuclei are sorted into their respective categories. In order to determine the relative contributions of the two processes to solar abundances, the s component is first extracted, being the more easily identified. Indeed, the product of the neutron capture cross-section with the abundance is approximately constant for aU the elements in this class. The figure shows that europium, iridium and thorium come essentially from the r process, unlike strontium, zirconium, lanthanum and cerium, which originate mainly from the s process. Other elements have more mixed origins. (From Sneden 2001.)... 

Explosive nucleosynthesis adds a few last trinkets to the abundance table, in particular, gold, platinum and uranium, through an ultimate nuclear process relating to neutron physics. 

The isotopic and elemental abundance table shows that, in the Solar System, iron is more abundant than its neighbours. Analysis of stellar spectra conhrms this result, giving it a universal character. 

We know today that nuclear statistical equilibrium in a neutron-poor environment (p/n = 1.01), dominated by nickel-56 rather than iron-56, gives a good overall explanation of the abundance table in the neighbourhood of the iron peak. This is a natural consequence of high-temperature combustion. The corresponding combustion times are... 

The chemical diversity of the world as reflected in Mendeleyev s periodic table and the elemental abundance table finally has its explanation. Today we have reached the stage where we can study the chemical evolution of the galaxies with a view to writing the story of each element in its own astrophysical context. Let us not forget the name of Beatrice Tinsley, who initiated this vision, but died too soon to witness its achievement. 

The term cosmochemistry apparently derives from the work of Victor Goldschmidt (Fig. 1.6), who is often described as the father of geochemistry. This is yet another crossover and, in truth, Goldschmidt also established cosmochemistry as a discipline. In 1937 he published a cosmic abundance table based on the proportions of elements in meteorites. He used the term cosmic because, like his contemporaries, he believed that meteorites were interstellar matter. Chemist William Harkins (1873-1951) had formulated an earlier (1917) table of elemental abundances - arguably the first cosmochemistry paper, although he did not use that term. As explained in Chapter 3, the term solar system abundance is now preferred over cosmic abundance, although the terms are often used interchangeably. 

Table 2.1 lists the principal stable isotopes of the common elements and their relative abundance calculated on the basis of 100 molecules containing the most common isotope. Note that this presentation differs from many isotope abundance tables, in which the sum of all the isotopes of an element adds up to 100%. 

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