Atomic Weights and Symbols

in our secular society, it is perhaps difficult to fully appreciate the importance of the vicarage in rural Europe as a nursery for future scientists and the bearer of an intellectual tradition in the rather austere cultural climate that prevailed there two centuries ago. At least, this was certainly true for Sweden, situated as it was in the outskirts of Europe, far from the cultural highroads. 

Jacob Berzelius (1779-1848) came from a family of clergymen and his father, who died when the boy was only four years old, was also ordained even if he worked as a teacher. His mother soon remarried the Rev. Anders Ekmarck, a widower with five children of his own. The boy grew up in a rural vicarage in the south of Sweden, not far from lake Vattem, but when he was eight years old he lost his mother to the same illness that had carried off his father, pulmonary 

One could perhaps say that Berzelius greatness as a scientist was his ability to create order out of confusion, rather than to come up with new ideas and theories, but there is one very important exception to this generalization. From 1821, he had 

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Cover Alchemist s Laboratory, David Lees/CORBIS Dalton s List of Atomic Weight and Symbols, Science Photo Library. 

Morveau appendices containing the nomenclature of some compound substances, which combine sometimes like simple bodies a memoir by de Fourcroy, explaining the tables of nomenclature (thirty-seven octavo pages) a directory of the new nomenclature in ninety-four pages, and the symbols prepared by Ilassenfratz and Adet, a chemical shorthand by which the names of elements and compounds could be replaced by symbols. This system never came into general use, and symbols, in so far as they were used by chemists, were of the already developed systems, until Dalton s concept of the atomic weights and symbols had been simplified by Berzelius (in 1815) into the system still in use. 

Figure 6-1. A portion of a list of atomic weights and symbols of the elements.

Dalton noticed that oxygen combined with nitrogen in a ratio of 1 to 1.7 and 1 to 3.4 by weight. After testing this observation many times, he proposed the law of multiple proportions, where element weights always combine in small whole number ratios. Dalton pubUshed his initial list of atomic weights and symbols in the summer of 1803, which formally gave chemistry the vocabulary (symbol names) that we have come to know and memorize. 

TABLE 2.2 Symbols, Atomic Weights, and Atomic Nnmbers of the Elements... 

For molecules Mr is the relative molecular mass or molecular weight for atoms Mr is the relative atomic mass or atomic weight and the symbol Ar may be used. Mr may also be called the relative molar mass, Mr>B = Mb/M, where M = 1 gmol-. The standard atomic weights, recommended by IUPAC, are listed in table 6.2, p.94. 

Table 6.2 lists the relative atomic masses of the elements in the alphabetical order of chemical symbols. The values have been recommended by the IUPAC Commission on Atomic Weights and Isotopic Abundances in 1991 [44] and apply to elements as they exist naturally on earth. 

The numbers in front of the symbols of the elements denote the atomic numbers the numbers underneath are the atomic weights. The latter are taken, with a few modifications, from the Report of the International Commission on Atomic Weights for 1932. The double arrow indicates the places where the order of atomic weights and that of atomic numbers do not agree. 

Stands, is shown in Fig. 49, which gives symbols, atomic weights, and group-numbers of the elements concerned ... 

Table 1.5. Periodic table of the elements (the data for each element are, from top to bottom, atomic number, atomic weight, chemical symbol, and common oxidation states in soils and plants)...

However, the conceptual battle betweenthe main characteristic of atoms of an element as atomic weight and atomic number lead with the Periodic System as one of the few universal symbols of nature instantly recognized worldwide, yet whose chemcial and physical roots are here to be restoried, with the hope of fresh impetus envisaging new atomic stractural revelations. 

Krypton is the name of Superman s home planet and also that of an element. Look up the element krypton and list its symbol, atomic number, atomic weight, and electron arrangement. 

The printed chart is nevertheless very useful for rapid assessment. For each element, there is the element symbol, atomic weight and thermal neutron absorption cross-section. Within the horizontal strip of isotopes, stable species are shown with a black background and contain the mass number, natural isotopic abundance of the... 

The symbols s and a denote functions which are symmetric and antisymmetric in the nuclei, respectively. Since it is known that protons and neutrons, as well as electrons, have spin the resultant nuclear spin is integral for even atomic weight and half-integral for odd atomic weight. For atoms with nuclear spin equal to zero, we can construct only one nuclear spin wave function o(I) o(2), where o(l) means that nucleus (1) has zero spin, etc. Th s wave function is symmetrical in the nuclei. Since zero spin can occur only for even atomic weight, we have the following corollary to the above rules ... 

Atomic number Element CAS Registry Number Symbol Atomic weight Discoverers and date of discovery... 

A similar activity is found in Mendeleevs first attempt at a periodic system as presented in a hand-written table. If one examines the calculations that he is carrying out one finds again an attempt to compute differences between the atomic weights of elements in the columns of his table. For example Mendeleev writes the number 27 in smaller writing below the symbols for potassium (Zn - K = 65 - 39 = 27) and again below rubidium (Cd-Rb = 112-85 = 27). 

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