Polar covalent bonds defined

In section 3.2, you learned about the strong bonds that hold ions in clearly-defined lattice patterns. You learned that these bonds are responsible for the properties of ionic compounds. You also learned how to describe the properties of compounds that are made up of molecules with covalent bonds. In this section, you discovered that the properties of compounds with polar covalent bonds depend on their shape. The following Concept Organizer summarizes some of the properties of covalent compounds that are made up of polar and non-polar molecules. 

How well can we tell the difference between an ionic bond and a polar covalent bond The only honest answer to this question is that there are probably no totally ionic bonds between discrete pairs of atoms. The evidence for this statement comes from calculations of the percent ionic character for the bonds of various binary compounds in the gas phase. These calculations are based on comparisons of the measured dipole moments for molecules of the type X—Y with the calculated dipole moments for the completely ionic case, X+Y. We performed a calculation of this type for HF in Section 13.3. The percent ionic character of a bond can be defined as... 

Polar covalent bonds can be regarded as having some degree of ionic character, and the distinction between ionic and covalent bond types is sometimes hard to make. Some compounds have clear examples of both types of bonding simultaneously. Thus CaC03 has well-defined carbonate ions... 

We define electronegativity as the ability of an atom in a compound to attract electrons to itself. In general, electron pairs are shared unequally between atoms with different electronegativities, leading to polar covalent bonds. 

This chapter will build on the principles just listed, in order to define covalent bonds and then extend this definition to discuss polarized covalent bonds. The hybridization model of covalent bonding will be introduced, as well as the concept of functional groups and the shape of molecules of the first two rows of the periodic table. 

Bonds may be partially ionic and partially covalent these bonds are called polar covalent bonds. Polar covalent bonds are defined more precisely in the next section. 

A polar covalent bond is defined in Section 12.4 as a bond in which bonding electrons are shared unequally. The charge density of the bonding electrons is shifted toward the more electronegative atom. 

Define the following terms, and identify the term that best describes the H—O bond in a water molecule non-polar covalent, polar covalent, ionic. 

Although Eq. 11 tries to take into account the effect of polar interactions, the role of acid/base interactions in adhesion became clear and theories describing them have been more and more accepted [35]. The boimdary case of such interactions is the formation of covalent bonds between the surfaces. Such interactions cannot be described by Eq. 11. As a consequence Fowkes [36] suggested that the reversible work of adhesion should be defined as ... 

Another point which needs to be clarified from the start is the nomenclature of metalated silanes We will frequently use the term silyl anion in this chapter when we talk about metalated silanes. Although the term anion defines, literally taken, an ionic compound, this expression, when used by us, does not necessarily imply that the compound in question is of ionic nature, but covers, as well, in analogy to the use of the term carbanion , silicon compounds with a polarized covalent silicon-metal bond. 

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