LIST OF ELEMENTS

This table includes the more common reagents used in gravimetric determinations. The lists of elements precip-... 

A Listing of Elemental Compositions vs. Accurate Mass at Nominal Integer Mass of 58... 

If the critical impurities are known, then only a selected list of elements need to be examined, with some improvement in the cost effectiveness of the analysis. However, the list of elements to be included in the qualification analysis is often historical and related to the limitations of the analytical methods previously used for qualification rather than for technological reasons related to the end use of the metal. As a result, problems in application can arise for no obvious reason. The time and cost of extending the impurity list for GDMS analysis to include essentially all elements is minimal, considering the additional information gained. 

Germanium and Sn appear about half-way down the list of elements in order of abundance in crustal rocks, together with several other elements in the region of l-2ppm ... 

In the periodic table, atomic masses are listed directly below the symbol of the element. In the table on the inside front cover of this text, atomic masses are cited to four significant figures. That ordinarily will be sufficient for our purposes, although more precise values are available (see the alphabetical list of elements on the inside back cover). 

Concerning (iii) Mendeleev, as is well known, produced different tables at different times. In fact, and as already mentioned, approximately sixty-five periodic tables were devised by Mendeleev not including partial tables and simple lists of elements. These sixty-five tables consist of published as well as unpublished manu-... 

The number of protons in an element s atomic nucleus is called the atomic number, Z, of that element. For example, hydrogen has Z = 1 and so we know that the nucleus of a hydrogen atom has one proton helium has Z = 2, and so its nucleus contains two protons. Henry Moseley, a young British scientist, was the first to determine atomic numbers unambiguously, shortly before he was killed in action in World War I. Moseley knew that when elements are bombarded with rapidly moving electrons they emit x-rays. He found that the properties of the x-rays emitted by an element depend on its atomic number and, by studying the x-rays of many elements, he was able to determine the values of Z for them. Scientists have since determined the atomic numbers of all the known elements (see the list of elements inside the back cover). 

All molar masses quoted in this text refer to these average values. Their values are given in Appendix 2D. They are also included in the periodic table inside the front cover and in the alphabetical list of elements inside the back cover. 

It is convenient to decompose the formula into a list of elements, removing the parentheses and including the atoms in the waters of hydration. 

A glance at the periodic table (which will be covered in detail in Chapter 5) shows a list of elements with numbers that are not as neat as those for carbon. Iron, for instance, has an atomic mass of 55.845. Could an atom have a fractional proton or neutron Of course not. An element must have a fixed number of protons. That is what defines it as an element. However, the number of neutrons in the nucleus of an element can vary. Carbon, for instance, has two prominent forms. Carbon 12 has 6 protons and 6 neutrons whereas carbon 14 has 6 protons and 8 neutrons. 

The list of elements and their species listed above is not exhaustive. It is limited to the relatively simple compounds that have been determined by an important number of laboratories specializing in speciation analysis. Considering the economic importance of the results, time has come to invest in adequate CRMs. There is a steadily increasing interest in trace element species in food and in the gastrointestinal tract where the chemical form is the determinant factor for their bioavailability (Crews 1998). In clinical chemistry the relevance of trace elements will only be fully elucidated when the species and transformation of species in the living system have been measured (ComeUs 1996 Cornelis et al. 1998). Ultimately there will be a need for adequate RMs certified for the trace element species bound to large molecules, such as proteins. 

The strangest section of the periodic chart comes in the first transition subgroup. Under scandium and yttrium (marked with stars on the periodic chart) fall two long horizontal lists of elements so much alike that they are squeezed into two squares of the chart. Elements with the atomic numbers 57-71 are called the lanthanides. The actinides are elements with the atomic numbers 89-103, and they are all radioactive. These transition elements are as follows ... 

TABLE 11.20 Elements Precipitated by General Analytical Reagents This table includes the more common reagents used in gravimetric determinations. The lists of elements precipitated are not in all cases exhaustive. The usual solvent for a precipitating agent is indicated in parentheses after its name or formula. When the symbol of an element or radical is italicized, die element may be quantitatively determined by the use of the reagent in question. ... 

Two methods of balancing reactions are of interest. We can balance reactions in terms of the stoichiometries of the species considered. In this case, the existing basis B is a list of elements and, if charged species are involved, the electron e. Alternatively, we may use a dataset of balanced reactions, such as the llnl database. Basis B, in this case, is the one used in the database to write reactions. We will consider each possibility in turn. 

The system is formally represented by a list of species, followed by a list of elements, both in arbitrary order ... 

Various databases can also be output by the interpreter, e.g. lists of element and species names, text files for labeling printed and plotted output, and a symbolic reaction matrix. This information is distributed to individual ASCII files, from which they may be read by subsequent parts of the simulation package for use in the appropriate task. 

List of Elements of the Periodic Table—Sorted by Abundance in Earth s crust. http //www. science.co. ilPTelements. asp s=Earth (accessed December 2, 2005). 

In qualitative analysis, the isotopic distribution remains an important information. For example in the case the parent drug contains Br or Cl, metabolites or decomposition products can be easily identified by considering the isotopic distribution. With accurate mass measurements a list of elemental compositions can be proposed for a compound for a given accuracy range. Because the intensity of the isotopic distribution is also dependent on the elemental composition of the molecule it can be used to reduce the list of possible elemental formulas [17]. 

When the French chemist Antoine Lavoisier published his famous list of elements in 1789, there were only 33 elements, several of which were erroneous. By 1930, the diligent labors of thousands of chemists had increased the tally of naturally occurring chemical elements to 90. More recently, physicists in high-energy laboratories have been able to create about 20 highly radioactive, unstable elements that do not exist naturally on Earth, although they are probably produced in the hot cores of some stars. 

In his list of elements Lavoisier mentioned thirty-three substances ... 

Lavoisier believed that it contained oxygen, and liad mentioned its radical in his list of elements (20). The first proof of the composition of boric acid was given in 1808 when Gay-Lussac and Thenard in France and Davy in England succeeded in decomposing it by reduction with... 

Many elements are present in the earth s crust in such minute amounts that they could never have been discovered by ordinary methods of mineral analysis. In 1859, however, Kirchhoff and Bunsen invented the spectroscope, an optical instrument consisting of a collimator, or metal tube fitted at one end with a lens and closed at the other except for a slit, at the focus of the lens, to admit light from the incandescent substance to be examined, a turntable containing a prism mounted to receive and separate the parallel rays from the lens and a telescope to observe the spectrum produced by the prism. With this instrument they soon discovered two new metals, cesium and rubidium, which they classified with sodium and potassium, which had been previously discovered by Davy, and lithium, which was added to the list of elements by Arfwedson. The spectroscopic discovery of thallium by Sir William Crookes and its prompt confirmation by C.-A. Lamy soon followed. In 1863 F. Reich and H. T. Richter of the Freiberg School of Mines discovered a very rare element in zmc blende, and named it indium because of its brilliant line in the indigo region of the spectrum. 

In the previous example, zinc was more easily oxidized than copper. The ability of one element to donate electrons to another element is based on the electron structure of the element and energy considerations. A spontaneous redox reaction, like any spontaneous reaction, results in a more stable configuration of the chemical system. The following list of elements shows how easily an element is oxidized. 

By the end of the seventeenth century, then, scientists were not really any closer to enumerating the elements than were the Greek philosophers. Yet a hundred years later the British chemist John Dalton (1766-1844) wrote a textbook that outlined a recognizably modern atomic theory and gave a list of elements that, while still very incomplete and sometimes plain wrong, is in content and in spirit a clear precursor to today s tabulation of the hundred and more elements. Why had our understanding of the elements changed so fast ... 

Bromine.—J. H. L. Vogt-5 estimates that bromine occupies about the 25th place in the list of elements arranged in the relative order of their abundance and that the total crust of the earth has about O OOl per cent, of bromine—the solid portion O OOOOl per cent. The ratio of bromine to chlorine is about the same in sea water and in the solid crust, and amounts to 1 150. The ratio of chlorides to... 

Neon occurs in the atmosphere to the extent of approximately 0.00182%, In terms of abundance, neon does not appear on lists of elements in the earth s crust because if does not exist in stable compounds. However, because of its limited solubility in H2O, neon is found in seawater to... 

The molar masses of elements are determined by using mass spectrometry to measure the masses of the individual isotopes and their abundances. The mass per mole of atoms is the mass of an individual atom multiplied by the Avogadro constant (the number of atoms per mole). However, there is a complication. Most elements occur in nature as a mixture of isotopes we saw in Section B, for instance, that neon occurs as three isotopes, each with a different mass. In chemistry, we almost always deal with natural samples of elements, which have the natural abundance of isotopes. So, we need the average molar mass, the molar mass calculated by taking into account the masses of the isotopes and their relative abundances in typical samples. All molar masses quoted in this text refer to these average values. Their values are given in Appendix 2D. They are also included in the periodic table inside the front cover and in the alphabetical list of elements inside the back cover. 

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