Lewis, Gilbert structures

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Covalent bonds form between atoms with similar electronegativities. In these reactions, electrons do not migrate from one atom to another as they do in ionic bonds they are shared by the atoms in the molecule. A good way to visualize this was proposed by Gilbert Lewis, a chemist at the University of California, Berkeley. His representations of molecular bonds are called Lewis dot structures. These structures use dots to denote the valence electrons of an element or molecule. 

Lewis, Gilbert Newton. 1923. Valence and the Structure of Atoms and Molecules. New York Chemical Catalog. 

Gilbert Newton Lewis described covalent bonds as sharing electrons in the 1910s and the electron pair donor/acceptor theory of acids and bases in the 1920s. Lewis dot structures and Lewis acids are named after him. 

The electronic and molecular geometries of covalent molecules, and hence their resulting polarities, can thus be predicted fairly accurately. Armed with these tools, one can predict whether or not a molecule should be soluble, reactive, or even toxic, see also Bonding Avogadro, Amedeo Bohr, Niels Cannizzaro, Stanislao Dalton, John Le Bel, Joseph-Achille Lewis, Gilbert N. Lewis Structures Pauling, Linus Thomson, Joseph John van t Hoff, Jacobus. 

FIGURE 318. The original Gilbert N. Lewis dot structures (Journal of the American Chemical Society, 38 762, 1916). 

Lewis, Gilbert Newton (1875-1946) American physical chemist who developed theories on chemical thermodynamics, atomic structure, and atomic bonding. He pioneered work on the electronic theory of valency, showing the difference between ionic and covalent bonds. He defined an acid as an electron acceptor and a base as an electron donor. 

Chemists often focus on the electrons in the outermost shell of the atom because these electrons are involved in the formation of chemical bonds and in chemical reactions. Carbon, for example, with the ground-state electron configuration 2 2p, has four outer-shell electrons. Outer-shell electrons are called valence electrons, and the energy level in which they are found is called the valence shell. To illustrate the outermost electrons of an atom, chemists commonly use a representation called a Lewis dot structure, named after the American chemist Gilbert N. Lewis (1875-1946), who devised it. A Lewis dot structure shows the symbol of the element surrounded by the number of dots equal to the number of electrons in the outer shell of an atom of that element. In Lewis dot structures, the atomic symbol represents the core (i.e., the nucleus and all inner shell electrons). Table 1.4 shows Lewis dot structures for the first 18 elements of the Periodic Table. 

Gilbert Newton Lewis (1875-1946 was born in Weymouth, Massachusetts, and received his Ph.D. at Harvard in 1899. After a short time as professor of chemistry at the Massachusetts Institute of Technology (1905-1912), he spent the rest of his career at the University of California at Berkeley (1912-1946). In addition to his work on structural theory, Lewis was the first to prepare heavy water," D20, in which the two hydrogens of water are the 2H isotope, ceuterium. 

Of great importance for the development of solution theory was the work of Gilbert N. Lewis, who introduced the concept of activity in thermodynamics (1907) and in this way greatly eased the analysis of phenomena in nonideal solutions. Substantial information on solution structure was also gathered when the conductivity and activity coefficients (Section 7.3) were analyzed as functions of solution concentration. 

The beginning of the twentieth century also marked a continuation of studies of the structure and properties of electrolyte solution and of the electrode-electrolyte interface. In 1907, Gilbert Newton Lewis (1875-1946) introduced the notion of thermodynamic activity, which proved to be extremally valuable for the description of properties of solutions of strong electrolytes. In 1923, Peter Debye (1884-1966 Nobel prize, 1936) and Erich Hiickel (1896-1981) developed their theory of strong electrolyte solutions, which for the first time allowed calculation of a hitherto purely empiric parameter—the mean activity coefficients of ions in solutions. 

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