Atomic weight, of the elements

Lead has only one form, a cubic metallic lattice. Thus we can see the change from non-metal to metal in the physical structure of these elements, occurring with increasing atomic weight of the elements carbon, silicon, germanium, tin and lead. 

Atomic Weights of the Elements Based on the Carbon 12 Standard... 

Numerical values for the atomic weights of the elements are now reviewed every 2 y by the Commission on Atomic Weights and Isotopic... 

The attention of the chemists had for many years been directed to the relations between the atomic weights of the elements and their respective physical and chemical properties and a considerable number of remarkable facts had been established by previous workers in this field of enquiry. 

In the various editions of his textbook, and in the publications dealing specifically with his predictions, Mendeleev repeatedly gives the example of calculating the atomic weight of the element selenium, a value that was known at the time and which could thus be used to test the reliability of his method. 

Perhaps the earliest hints of any numerical regularity among the atomic weights of the elements was discovered as early as 1817 by Dobereiner. He was the first to notice the existence of various groups of three elements, subsequently called triads, that showed chemical similarities. In addition, such elements displayed an important numerical relationship, namely that the equivalent weight, or atomic weight, of the middle element is the approximate mean of the values of the two flanking elements in the triad. 

The substances we call elements are composed of atoms. Atoms in turn are made up of neutrons, protons and electrons neutrons and protons in the nucleus and electrons in a cloud of orbits around the nucleus. Nuclide is the general term referring to any nucleus along with its orbital electrons. The nuclide is characterized by the composition of its nucleus and hence by the number of protons and neutrons in the nucleus. All atoms of an element have the same number of protons (this is given by the atomic number) but may have different numbers of neutrons (this is reflected by the atomic mass numbers or atomic weight of the element). Atoms with different atomic mass but the same atomic numbers are referred to as isotopes of an element. 

A complete list of the modern values of the atomic weights of the elements is given in Table 3-1. 

There are several forms in which the elements of the periodic chart may be arranged. The version shown here is one of the forms now in widespread use. Groups I, II, III, etc., and the noble gases are called the Main Group Elements. All of their inner shells are fully occupied with electrons. The other elements are called the Transition Elements. They all have at least one inner shell that is only partially filled with electrons. Referring to the entire table, the numbers written above the symbols of the elements (always whole numbers) are the atomic numbers of the elements, and the numbers written below the symbols of the elements (not necessarily whole numbers) are the atomic weights of the elements. Parentheses indicate insufficient information exists or material is not yet official. 

To get the final answer, we must divide the energy released by the moles of glucose. We find the moles of glucose from the mass given in the problem and the molar mass determined from the atomic weights of the elements. 

Dissertation, Universitat Gottingen, Gottingen, Germany Collins AG (1976) Lithium abundances in oilfield waters. Itr. Lithium Resources and Requirements by the Year 2000. Vine JD (ed) U.S. Geol Surv Prof Pap 1005 116-123 Coplen TB (1996) Atomic weights of the elements 1995. Pure Appl Chem 68 2339-2359... 

In order to successfully interpret a mass spectrum, we have to know about the isotopic masses and their relation to the atomic weights of the elements, about isotopic abundances and the isotopic patterns resulting therefrom and finally, about high-resolution and accurate mass measurements. These issues are closely related to each other, offer a wealth of analytical information, and are valid for any type of mass spectrometer and any ionization method employed. (The kinetic aspect of isotopic substitution are discussed in Chap. 2.9.)... 

Atomic weights are those of the most commonly available long-lived isotopes on the 1999 lUPAC Atomic Weights of the Elements A value given in square brackets denotes the mass number at the longest-lived isotope... 

Carbon-12 is the basis for the average atomic mass units (amu) that is used to determine the atomic weights of the elements. Carbon is one of the few elements that can form covalent bonds with itself as well as with many metals and nonmetals. 

In 1869 Mendeleev s paper on the periodic law, On the Relation of the Properties to the Atomic Weights of the Elements, was read... 

Dalton s application of the Greek atomic theory to the facts established by the analyses of compounds enabled him to attach to each element a number which he called the atomic weight of the element, and to summarise all the facts concerning the compositions of compounds in the statement, that the elements combine in the ratios of their atomic weights, or in the ratios of whole multiples of their atomic weights. All the investigations which have been made into the compositions of compounds, since Dalton s time, have confirmed the generalisation which followed from Dalton s application of the atomic theory. 

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