Notions of Chemistry

Pelouze and E. Fremy, Notions Genercdes de Chimie. Avec un Atlas de 24 Planches en Couleur, en 2 Volumes, Victor Masson, Paris, 1853. The plates shown here are from the American edition General Notions of Chemistry, Lippincott, Grambo Co., Philadelphia, 1854. 

The Development of Modern Chemistry, Harper Row, New York, 1964, p. 451. 

FIGURE 253. Black and white image of a color plate from the 1854 American edition of Notions Generale de Chimie by Pelouze and Fremy. See color plates. Depicted in J 0 is an industrial-scale still consisting of a copper boiler covered with a hood 11 displays the very modem-looking water-cooled distillation apparatus designed by Gay-Lussac. 

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Lavoisier s program and the new chemistry were seen by many to constitute a statement of the centrality of chemistry, rather than "physics" or "natural philosophy," to the sciences as a whole. The notion of chemistry as a "central science" is found in the hierarchy of the sciences outlined by Comte in the early nineteenth century. It can be observed later in the mapping of the structure of twentieth-century science, in which the sociologist Eugene Garfield, for example, identifies the three disciplinary poles of physics, chemistry, and biomedicine, in which "chemistry functions as a critical point of integration for much of the natural sciencesa hypothesis that is supported further by the very weak connection between physics and biomedicine. "30... 

One of the most deeply held notions of chemistry is the concept of chemical bond. Such bonds, almost always depicted as formal lines between atomic symbols, have their counterpart within the quantum chemical description of electron densities often [45-51], but not always [54-60], a correspondence can be made between conventional chemical bonds and specific lines defined by the electron density gradient maps. These lines usually interconnect nuclear positions. However, as has been pointed out by Cioslowski [54-60], there are cases where this correspondence fails. 

The notions of chemistry and quantum theory are in a state of conflict. Indeed, it must be said that quantum mechanics and traditional chemistry contradict each other at a very fundamental level. Whereas traditional chemistry claims that each nucleus in a molecule is located at some particular (possibly fluctuating) position in space, quantum mechanics asserts that nuclei within a molecule need not have a dispersion-free position at all. 

To have compared nitrogen with antimony, with boron, or even with chlorine, might up to a certain point have been conceivable, but to imagine that chlorine, the most negative of all bodies, could fulfil the functions of the highly positive hydrogen, was to misunderstand the most elementary notions of chemistry. 

Cros, D., Chastrette, M., Fayol, M. (1987). Conceptions of second year university students of some fundamental notions of chemistry. International Journal of Science Education, 10, 331-336. 

The notion of chemistry in vocational education conjures up many professions and occupations that do or may involve some knowledge of chemistry. Academic chemistry, industrial chemistry, analytical chemistry, pharmacy, chemical engineering, mining and metallurgy and chemistry teaching are obvious chemical professions. Environmental science, materials engineering and forensic science are less obvious professions that involve substantial chemistry. 

Imitating the corresponding notion of chemistry, we call it the valence off. The other sum is... 

Another important concept is the notion of stabilization by means of coordination, A classic example is the. stabilization of the fugitive species cyclobutadiene, C4H4I by coordination to (Fe(CO)3l (p. 936). As the C atom is isoclectronic with (BH], so (C4H4] is isoelectronic with the borane fragment (BaH which is similarly stabilized by coordination to (Fe(CO)3l or the isoelectronic (Cofr/ -CsHs)) (see Panel on p. 174), Indeed it is a general feature of metallaboranc chemistry that such clusters are often much more stable than are the parent boranes themselves. 

Closely related to the concept of chirality, and particularly important in biological chemistry, is the notion of prochirality. A molecule is said to be prochiral if can be converted from achiral to chiral in a single chemical step. For instance, an unsymmetrical ketone like 2-butanone is prochiral because it can be converted to the chiral alcohol 2-butanol by addition of hydrogen, as we ll see in Section 17.4. 

Of course, nowadays, as every student of chemistry and physics knows, electron orbits have been replaced by orbitals that are supposed to be smeared out in space. But this view misses the point somewhat and is not the whole lesson from quantum mechanics. The more radical lesson is that even these probability-based orbitals simply do not exist. The notion of assigning four quantum numbers to each electron is just an approximation, albeit a powerful one. 

The expert is aware that the electron s history has no significance, but a learner may well expect there to be a greater attraction between an atomic core and the bonding electron that belongs to that atom (Taber, 1998). Such beliefs may seem rather bizarre for those used to thinking of chemistry in terms of fundamental concepts (such as energy and forces), but actually reflect one of the basic principles of magic that seem to commonly influence people s intuitions about the natural world (Nemeroff Rozin, 2000). Indeed the notion that a past association leaves some... 

For students to make sense of the basic grammar of chemical equations they need to appreciate the concept of the chemical reaction. This, in turn, requires an understanding of the notion of chemical snbstance. Although these are basic concepts in chemistry, they are known to present difficulties to many learners. 

The notions of mass balance, selectivity and conversion (see Figure 1.6) need to be added to the idea of yield when chemists consider a chemical transformation, particularly if this consideration takes place in the context of pollution prevention or green chemistry. ... 

The science of chemistry languished until Robert Boyle—a brilliant, fanatically religious man—wrote The Sceptical Chymist in 1661. He gave scientists a new way of seeing the world by defining an element as any substance that could not be broken down into a simpler substance, an idea that closely coincides with todays notion of an element. Boyles insight led chemists into their labs, where they heated solids and evaporated liquids and analyzed the gases that boiled off and the residues that remained behind. They isolated a flood of new elements. 

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