Atomic abundance

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... 

Using this approach the relative atomic abundances of light elements in the specimen are easily determined. 

Here M/H is the atomic abundance, My/M is the proportion of M atoms in the appropriate state of excitation and ionization to absorb the line, a(Av) is the selective absorption cross-section implied by Eq. (3.27) and ak the continuous absorption cross-section per hydrogen atom this latter is related to kx (e.g. as in Table 3.2) by the number of H atoms per gram. 

Table 4.7. Atomic abundance of selected isotopes of Yb and GdO at mass m.

Table 4.8. Atomic abundance of isotopes of mass m in natural and spike Nd.

Many molecules contain chemically equivalent atoms, which, though in a different crystal environment, have, to a good approximation, the same electron distribution. Such atoms may be linked, provided equivalent local coordinate systems are used in defining the multipoles. In particular, for the weakly scattering hydrogen atoms, abundant in most organic molecules, this procedure can lead to more precisely determined population parameters. 

Element A Atom % Abundance Process Element A Atom% Abundance Process... 

Fig. I. (a) Atomic abundances relative to Si = Iff versus atomic weight for die sun and similar main-sequence stars, (b) Cross-section factor S (in MeV-vams) versus cenler-of-momcnlum energy (in MeV) for l C(rt. y lO Dashed and solid curves are theoretical extrapolations of Munster and Kellog Caltech data by Langanke and Koonin (see references). 1 After paper on "The Quest for the Origin of the Elements by William A. Fowler, presented in December 1983, when author received the Nobel Prize for Physics. Complete article in Science. 226, 922-935 (November 23. 1984) and in Les Prix Nobel en 1983," Elsevier, New York, 1984]...

Figure 12.4 Atomic abundances of the elements in the solar system and the major nucleosynthetic processes responsible for the observed abundances. [From E. M. Burbidge, et al., Rev. Mod. Phys. 29, 547 (1957). Copyright (1957) by the American Physical Society.]...

Table III. Order of Atomic Abundance" of the Most Common Elements and Their Oxidation States in the Upper Lithosphere...

Isotope Isotopic Ratios" Isotopic Ratios (alternate) Percent atomic Abundance Total abundance (cm3 STP/g)6... 

C = concentration W = weight A = atomic weight a = atomic abundance R = ratio... 

Interstellar Li isotopes Atomic abundances are also measured in interstellar clouds along the line of sight to stars. Their absorption produces a diminution of the light at the wavelength of the isotopes in question, and its magnitude reflects the interstellar abundance. Only recently has spectrograph resolution become accurate enough... 

Table 1 Atomic abundances of major elements (relative to silicon). ...

Earth, relative to average solar system (chondrites). However, the tungsten isotopic difference between early metals and the silicate Earth on its own does not provide constraints on timing. One needs to know the atomic abundance of Hf at the start of the solar system (or the ( Hf/ Hf)Bssn the bulk solar system initial ) and the composition of the chondritic reservoirs from which most metal and silicate reservoirs were segregated. In other words, it is essential to know to what extent the extra in the silicate Earth relative to iron meteorites accumulated in the accreted chondritic precursor materials or proto-Earth with an HfAV 1 prior to core formation, and to what extent it reflects an accelerated change in isotopic composition because of the high HfAV ( 15) in the silicate Earth. 

Table 4 Relative atomic abundances in gas and dust at comet Halley.

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