Chemical bonds Lewis structures

In 1912 he became the chair of the chemistry department at the University of Cah-fomia at Berkeley, which he turned into a renowned center of chemical research and teaching. In 1916 he published his theory of the shared electron-pair chemical bond (Lewis structures), a concept he had been thinking about since at least 1902. In the course of measuring the thermodynamic properties of electrolyte solutions, he introduced the concept of ionic strength (1921). 

Lewis s interest in chemical bonding and structure dated from 1902. In attempting to explain "valence" to a class at Harvard, he devised an atomic model to rationalize the octet rule. His model was deficient in many respects for one thing, Lewis visualized cubic atoms with electrons located at the corners. Perhaps this explains why his ideas of atomic structure were not published until 1916. In that year, Lewis conceived of the... 

Synthesis and drug design Bonding, Lewis structures, chemical reactions, microbiology Drug development... 

This chapter explains how the basic ideas of chemical structure and bonding apply to organic molecules. Most of it is a review of topics that you covered in your general chemistry courses, including molecular bonds, Lewis structures and resonance, atomic and molecular orbitals, and the geometry around bonded atoms. 

The opening paragraph of this chapter emphasized that the connection between structure and properties is what chemistry is all about We have just seen one such con nection From the Lewis structure of a molecule we can use electronegativity to tell us about the polarity of bonds and combine that with VSEPR to predict whether the mol ecule has a dipole moment In the next several sections we 11 see a connection between structure and chemical reactivity as we review acids and bases... 

Lewis structure (Section 1 3) A chemical formula in which electrons are represented by dots Two dots (or a line) be tween two atoms represent a covalent bond in a Lewis structure Unshared electrons are explicitly shown and sta ble Lewis structures are those in which the octet rule is sat isfied... 

The Lewis structure of a molecule shows atoms by their chemical symbols, covalent bonds by lines, and lone pairs by pairs of dots. For example, the Lewis structure of HF is H - F . We shall see that Lewis structures are a great help in... 

There remains one topic to be discussed in our survey of chemical bonding in organic compounds. For most compounds, all the molecules have the same structure, whether or not this structure can be satisfactorily represented by a Lewis formula. But for many other compounds there is a mixture of two or more structurally distinct compounds that are in rapid equilibrium. When this phenomenon, called tauto-merism, exists, there is a rapid shift back and forth among the molecules. In most cases, it is a proton that shifts from one atom of a molecule to another. 

A central feature of a Lewis structure is the bonding framework, which shows all the atoms connected as they are in the actual molecule. There is no foolproof method for putting the atoms together in the correct arrangement, but the following guidelines frequently lead from the chemical formula to the correct arrangement of atoms. 

It is essential to realize that electrons In the nitrate anion do not flip back and forth among the three bonds, as implied by separate structures. The true character of the anion is a blend of the three, In which all three nitrogen-oxygen bonds are equivalent. The need to show several equivalent structures for such species reflects the fact that Lewis structures are approximate representations. They reveal much about how electrons are distributed in a molecule or ion, but they are imperfect instruments that cannot describe the entire story of chemical bonding, hi Chapter 10, we show how to interpret these structures from a more detailed bonding perspective. 

The Lewis stmcture of a molecule shows how the valence electrons are distributed among the atoms. This gives a useful qualitative picture, but a more thorough understanding of chemistry requires more detailed descriptions of molecular bonding and molecular shapes. In particular, the three-dimensional structure of a molecule, which plays an essential role in determining chemical reactivity, is not shown directly by a Lewis structure. 

A description of the bonding in triethylaluminum begins with the Lewis structure. The chemical formula,... 

Determine the chemical formulas and Lewis structures of these two substances. Describe then-bonding completely, including the geometry and hybridization for each carbon atom. 

By taking Eq. (1.33) as the starting unperturbed Eq. (1.2), one can analyze delocalization corrections to the localized Lewis structure picture by the perturbative formalism of Eqs. (1.3)-(1.5) and Section 1.4. Valency and bonding phenomena can thereby be dissected into localized and delocalized contributions in a numerically explicit manner. This, in overview, is the strategy to be employed for chemical phenomena throughout this book. 

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