Chemical bonding electronegativity

Types of Chemical Bonds electronegativity Bond Polarity and Dipole Moments Ions Electron Configurations and Sizes Predicting Formulas of Ionic Compounds Sizes of Ions... 

Electronegativity and Polarity Electronegativity refers to the relative ability of elements to attract electrons within a chemical bond. Electronegativity increases as you move to the right across a period in the periodic table and decreases as you move down a column. When two nonmetal atoms of different electronegativities form a covalent bond, the electrons in the bond are not evenly shared and the bond is polar. In diatomic molecules, a polar bond results in a polar molecule. In molecules with more than two atoms, polar bonds may cancel, forming a nonpolar molecule, or they may sum, forming a polar molecule. 

Another fundamental property of chemical bonds is polarity. In general, it is to be expected that the distribution of the pair of electrons in a covalent bond will favor one of the two atoms. The tendency of an atom to attract electrons is called electronegativity. There are a number of different approaches to assigning electronegativity, and most are numerically scaled to a definition originally proposed by Pauling. Part A of Table 1.6... 

Two types of chemical bonds, ionic and covalent, are found in chemical compounds. An ionic bond results from the transfer of valence electrons from the atom of an electropositive element (M) to the atom(s) of an electronegative element (X). It is due to coulombic (electrostatic) attraction between the oppositely charged ions, M (cation) and X (anion). Such ionic bonds are typical of the stable salts formed by combination of the metallic elements (Na, K, Li, Mg, etc.) with the nonmetallic elements (F, Cl, Br, etc.). As an example, the formation of the magnesium chloride molecule from its elemental atoms is shown by the following sequence ... 

On the other hand, fluorine s high electronegativity and its ability to form mostly ionic chemical bonds, provide materials with several useful properties. First, compared to oxides, fluoride compounds have a wide forbidden zone and as a result, have low electroconductivity. In addition, fluorides are characterized by a high transparency in a wide optical range that allows for their application in the manufacturing of electro-optical devices that operate in the UV region [42,43]. 

THE NATURE OF THE CHEMICAL BOND. IV. THE ENERGY OF SINGLE BONDS AND THE RELATIVE ELECTRONEGATIVITY... 

The Nature of the Chemical Bond Fifty Years Later The Relative Electronegativity of Atoms Seen in Perspective... 

One of the most pervasive ideas to emerge from the series of papers entitled The Nature of the Chemical Bond is the concept of the relative electronegativity of atoms. The sections that follow examine some of the consequences of this concept. 

The quantum mechanical argument used in deriving the original electronegativity scale involved the amount of ionic character of a normal covalent bond A—B, and it was evident that the amount of ionic character and accordingly the value of the electric dipole moment of the bond would be closely correlated with the difference Ax = xA — xB of the two atoms A and B. In the first edition of The Nature of the Chemical Bond (1939) the following equation was advanced ... 

Table 1-1 gives the values of the Mulliken electronegativity, the results of dividing these values by 2.69, and the values from The Nature of the Chemical Bond. (The factor 2.69 is the ratio of the sum of the first-row values to the sum of the third-row values.) The second reason for the failure to obtain a correlation is neglect of some of the structural features. Let us consider the factor 2.69 now. 

Our work described in this section clearly illustrates the importance of the nature of the cations (size, charges, electronegativities), electronegativity differences, electronic factors, and matrix effects in the structural preferences of polar intermetallics. Interplay of these crucial factors lead to important structural adaptations and deformations. We anticipate exploratory synthesis studies along the ZintI border will further result in the discovery of novel crystal structures and unique chemical bonding descriptions. 

Electronegativity measures how strongly an atom attracts the electrons in a chemical bond. This property of an atom involved in a bond is related to but distinct from ionization energy and electron affinity. As described in Chapter 8, ionization energy measures how strongly an atom attracts one of its own electrons. Electron affinity specifies how strongly an atom attracts a free electron. Figure 9 6 provides a visual summary of these three... 

Electronegativities, which have no units, are estimated by using combinations of atomic and molecular properties. The American chemist Linus Pauling developed one commonly used set of electronegativities. The periodic table shown in Eigure 9 7 presents these values. Modem X-ray techniques can measure the electron density distributions of chemical bonds. The distributions obtained in this way agree with those predicted from estimated electronegativities. 

Cyclic systems have frequently been used in studies of chemical bonding and reactivity, reaction mechanisms and a variety of other problems of interest to chemists. Their utility depends on the changes in the carbon-carbon and the carbon-heteroatom bonds as well as on steric and electronic effects that result from the introduction of heteroatoms into the system. Indeed, the carbon-heteroatom bond length in small rings shows an effective increase with increasing heteroatom electronegativity, in line with a... 

Atoms in a molecule are joined by bonds. Bonds are formed when the valence or outermost electrons of two or more atoms interact. The nature of the bond between atoms goes a long way toward determining the properties of the molecule. Chapter 5 introduced the two common types of chemical bonds covalent and ionic. Elements with similar electronegativities share electrons and form covalent bonds. But elements with greatly different electronegativities exchange one or more electrons. This is called an ionic bond. 

Electronegativity A measure of the attracting power of an atom for an electron in a chemical bond. 

The electronegativity of an element indicates the relative ability of its atoms to attract electrons to form chemical bonds. According to the graph, as yon move across a period in the periodic table —... 

Since the elastic stiffness is related to the electronegativity difference density (Gilman, 2003) so is the hardness. Thus, like the covalent solids, the hardnesses of the alkali halides depends on the strength of the chemical bonding within them. 

For a fundamental vibrational mode to be IR-active, a change in the molecular dipole must take place during the molecular vibration. This is described as the IR selection rule. Atoms that possess different electronegativity and are chemically bonded change the net dipole of a molecule during normal molecular vibrations. Typically, antisymmetric vibrational modes and vibrations due to polar groups are more likely to exhibit prominent IR absorption bands. 

Electronegativity is defined as the tendency of an atom to attract electrons to itself in a chemical bond. 

A chemical bond exhibiting 100% covalent character and 0% ionic character occurs between identical nonmetals atoms in which the difference in electronegativity (AEN) is zero. An example is the H-H bond. There are atoms with essentially the same electronegativity, e.g. N and Cl both have an electronegativity equal to 3.0 to 2 significant figures, so the N-Cl bond would exhibit close to 100% covalent character and 0% ionic character . 

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