Covalent bond partial ionic character

It has been pointed out4 that bonds between non-identical atoms may be considered to resonate between a covalent and an ionic structure, the bond in this way having partially covalent and partially ionic character. The resonance energy of this effect, which is usually essentially the same for a given bond in different molecules, is included in the values given for the bond energies in the nonresonating molecules discussed. 

As we ve just seen, if you ask Is an X—Y bond ionic or covalent the answer in almost every case is Both, partially A better question is 7b what extent is the bond ionic or covalent The partial ionic character of a bond is related directly to the electronegativity difference (AEN), the difference between the EN values of the bonded atoms a greater AEN results in larger partial charges and a higher partial ionic character. Consider these three chlorine-containing molecules AEN for LiCl(g) is 3.0 - 1.0 = 2.0 for HCl(g), it is 3.0 - 2.1 = 0.9 and for CElg), it is 3.0 - 3.0 = 0. Thus, the bond in LiCl has more ionic character than the H—Cl bond, which has more than the Cl—Cl bond. 

Polar covalent bonds are covalent bonds with ionic character (partial election transfer). Ionic and covalent bonding are extremes forms of bonding polar bonds are intermediate in nature. The larger the difference in electronegativity between the atoms, the greater the polarity of the... 

The previous literature on the effects of partial covalence on interatomic distances is contradictory. Pauling (1960) cites the examples of CuF, BeO, AIN, and SiC where observed bond lengths are shorter than the sum of the covalent radii. He attributes these differences to partial ionic character and thus implies that partial ionic character shortens covalent bonds. This conclusion is in accord with the Schoemaker— Stevenson (1941) rule Dab = a + pb—C nx— b where > interatomic distance between A and B, rx and r = covalent radii of A and B, a and xb = electronegativity of A and B and C = constant. 

When two atoms share electrons unequally, it means that the bond between them is polar. Another way to describe this is to say that the bond has partial ionic character. For the molecule AB, this is equivalent to drawing two structures, one of which is covalent and the other ionic. However, there are actually three structures that can be drawn... 

Because the Cl atom is more electronegative than the H atom, the bond pair is pulled towards the Cl atom. This results in a covalent bond with some partial ionic character the small charges present are indicated by a 8. 

Such an off-center covalent bond displays partial ionic character. 

Eormula HE MW 20.006. A very stable polar covalent diatomic molecule H—E bond energy 136.1 kcaPmol at lower temperatures molecules are associated by hydrogen bonding H—bond length 0.92A partial ionic character 40% dipole moment 6.10 D hydrofluoric acid is an aqueous solution of hydrogen fluoride gas. 

Let us discuss the importance of charge separation in bonds involving atoms of different electronegativity, for example, C and N, O, or Cl. The extent of partial ionic character in such polar covalent bonds is a key factor in determining a compound s... 

The Partial Ionic Character of Covalent Bonds and the Relative Electronegativity of Atoms... 

Instead of using this description of the bond as involving resonance between an extreme covalent bond H C1 and an extreme ionic bond H+Cl-, we may describe the bond as a covalent bond with partial ionic character, and make use of the valence line, writing H—Cl (or H—Cl )... 

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