Chemists Alternative Definitions

Metallurgists were automatically combined with chemists in the 1970 Census coding. This means that even in the most disaggregated, unpublished 

Male chemists in 1960 (according to the 1970 system) X 0.87266 = Male chemists in 1960 (according to the 1960 system). 

Applying the conversion factors and rounding to the nearest thousand yields a total of 98 000 chemists in the labor force in 1970, not counting 

The conversion percentages given below are from 19, Table 1. (See ibid., 4-5, for a discussion of the standard error of these estimates.) 

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In the same year that Bronsted and Lowry proposed their definition of acids and bases, an American chemist named Gilbert Lewis proposed an alternative definition that not only encompassed Bronsted-Lowry theory but also accounted for acid-base reactions in which a hydrogen ion isn t exchanged. Lewis s definition relies on tracking lone pairs of electrons. Under his theory, a base is any substance that donates a pair of electrons to form a coordinate covalent bond with another substance, while an acid is a substance that accepts that electron pair in such a reaction. As we explain in Chapter 5, a coordinate covalent bond is a covalent bond in which both of the bonding electrons are donated by one of the atoms forming the bond. 

Physical organic chemists have tended to examine parameters based on shifts in the absorption peaks in the spectra of various dyes or indicator molecules. The a and P scales of Taft and Kamlet, the ET(30) scale of Dimroth and Reichardt, the 7t scale of Taft and co-workers and the Z value of Kosower are all examples of this type of parameter. The definitions and measurement means for these parameters, as well as important references, are shown in Table 5. An alternative definition of the Dimroth-Reichardt parameter is the dimensionless, ETN, which is now preferred by some organic chemists (for a discussion see Ref. 15). The Z value is important in that it led to the scale of Dimroth and Reichardt, which overcomes many of the limitations of the earlier scale. Several workers have shown that relationships exist, with good correlation coefficients, between similar parameters. Thus, DN is linearly related to p, both parameters being designed to measure the donor properties (or Lewis basicity) of solvent molecules. Also, Lr(30) is related to a as well as to AN all three parameters purport to measure the electron acceptor properties (or Lewis acidity) of solvent molecules. It has been found that different solvent types have different coefficients in linear relationships between n and the dipole moment. The Taft and Dimroth-Reichardt parameters, in particular, have been found to correlate with free energies and... 

Two years after Pauling defined electronegativity, the American chemist Robert Mulliken proposed an alternate definition in which the electronegativity for an element... 

Measures of chemistry as an occupation may be derived from several sources. Among them, the reports of the U.S. Bureau of the Census offer the most carefully defined, most homogeneous, and longest time series on the aggregate level. This section will be based primarily upon Census information with discussion, when appropriate, of both variant estimates for and alternative definitions of the occupation of chemist. ... 

A concept can also be operational in a different sense. Thus, the designated entity can be defined in terms of the operations it can perform. Lavoisier points to this alternative definition when he says of his elements that they act with regard to us as simple substances . What is important for him as a chemist is that the elements are actors in chemical operations, and so are defined by how they act and react in a network of relations with respect to other chemical actors. This second sense of operational definition is more fundamental than the first, and was characteristic of chemistry even before Lavoisier introduced this explicitly pragmatic definition of the element. 

A series of observations in which the presence of an apparently unaffected substance initiated the progress of a chemical reaction prompted the Swedish chemist Berzelius in 1835 to introduce the term catalyst , but it was only towards the end of the last century that a dear definition could be given by Ostwald, namely a catalyst is a substance which affects the rate of a chemical reaction without appearing in the final products . This is achieved through the formation of intermediate compounds between the catalyst and the molecules involved in the reaction whereby an alternative path is offered which may be passed through with higher probability, i.e. 

In the meantime, the great French chemist Claude Louis Berthollet (1748-1822) had by 1801 arrived at the conclusion that chemical elements could react in different proportions so that the resulting compound could represent a continuum of proportions of its constituent elements (atoms). This led to a conflict between him and Proust, who in 1804 published results on metallic oxides, which indicated that Berthollet s results were caused by this investigator having analyzed mixtures of two oxides, or alternatively, of the metal and one of its oxides. The dispute continued for several years and it would seem that the two combatants held to their views until the end of their lives. Nevertheless, there can be no doubt that, by introducing the principle of definite proportions of the elements in a chemical compound, Proust has made a major contribution to modern chemistry. 

There is no quantum-mechanical evidence for spatially directed bonds between the atoms in a molecule. Directed valency is an assumption, made in analogy with the classical definition of molecular frameworks, stabilized by rigid links between atoms. Attempts to rationalize the occurrence of these presumed covalent bonds resulted in the notion of orbital hybridization, probably the single most misleading concept of theoretical chemistry. As chemistry is traditionally introduced at the elementary level by medium of atomic orbitals, chemists are conditioned to equate molecular shape with orbital hybridization, and reluctant to consider alternative models. Here is another attempt to reconsider the issue in balanced perspective. 

But this definition is compatible with what chemists of the l600s viewed as elements as well as the modern view, so it is doubtful that Boyle meant anything new. He likewise offered no new list of what should be considered an element, but this may be to his credit. Boyle knew the definitions were faulty, but he did not feel on firm enough experimental ground to offer an alternative. He did however hypothesize that there could be more than four elements and even perhaps more than five. He would have been interested to know that today we list 109, and we are looking for more. 

Despite of some misunderstandings in the discussion about a proper definition of photocatalysis, photocatalytic reactions have captured the interest of chemists for a long time. Furtheron, photocatalysis has preserved its fascination as a method that not only provides a real alternative of usual chemical synthetic pathways [37]. Other promising fields of application of photocatalysis are the conversion of solar energy into chemical energy [38], information recording [39], and environmental problems like waste water decontamination [40]. 

Resource Material for Other Courses. There are numerous opportunities for the introduction of alternative problems and laboratory exercises in other standard chemistry courses, or for supplementary lecture material. Instructors are challenged to develop their own contributions to the education of the OSHA Savvy Chemist. While a single definitive source remains to be written, there are many sources of information that could be useful. A few possibilities are given below ... 

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